diff --git a/devtools/client/aboutdebugging/aboutdebugging.js b/devtools/client/aboutdebugging/aboutdebugging.js
index 9e69828dcf5..a8a79fc7898 100644
--- a/devtools/client/aboutdebugging/aboutdebugging.js
+++ b/devtools/client/aboutdebugging/aboutdebugging.js
@@ -105,7 +105,7 @@ var AboutDebugging = {
     DebuggerServer.allowChromeProcess = true;
     this.client = new DebuggerClient(DebuggerServer.connectPipe());
 
-    this.client.connect(() => {
+    this.client.connect().then(() => {
       // Show the first available tab.
       this.showTab();
       window.addEventListener("hashchange", () => this.showTab());
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_addonactor.js b/devtools/client/debugger/test/mochitest/browser_dbg_addonactor.js
index d35fa8f3d88..2a5e3b6a292 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_addonactor.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_addonactor.js
@@ -16,7 +16,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-01.js b/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-01.js
index 5737d3df77e..de28962ce73 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-01.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-01.js
@@ -17,7 +17,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-02.js b/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-02.js
index f09d858c46c..15ea48e6bd2 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-02.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-02.js
@@ -18,7 +18,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-03.js b/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-03.js
index 38e72a80da3..a054b93c432 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-03.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_break-on-dom-event-03.js
@@ -17,7 +17,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_chrome-debugging.js b/devtools/client/debugger/test/mochitest/browser_dbg_chrome-debugging.js
index 6005a430263..8c02cdd9dee 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_chrome-debugging.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_chrome-debugging.js
@@ -27,7 +27,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_debugger-statement.js b/devtools/client/debugger/test/mochitest/browser_dbg_debugger-statement.js
index 64bba61b239..5cc7e1c435f 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_debugger-statement.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_debugger-statement.js
@@ -18,7 +18,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-01.js b/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-01.js
index 930165b253c..1755ac9e268 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-01.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-01.js
@@ -18,7 +18,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-02.js b/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-02.js
index f6b8268e2af..2b4b74fdcc9 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-02.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-02.js
@@ -19,7 +19,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-03.js b/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-03.js
index b44e3f9bcb2..6b58d773b95 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-03.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_event-listeners-03.js
@@ -19,7 +19,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_globalactor.js b/devtools/client/debugger/test/mochitest/browser_dbg_globalactor.js
index 9c3ad076da2..70971aa9474 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_globalactor.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_globalactor.js
@@ -20,7 +20,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_listaddons.js b/devtools/client/debugger/test/mochitest/browser_dbg_listaddons.js
index 212cda90eb7..fa44a1261f0 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_listaddons.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_listaddons.js
@@ -17,7 +17,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_listtabs-01.js b/devtools/client/debugger/test/mochitest/browser_dbg_listtabs-01.js
index 607357dcd4b..f3378f8050c 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_listtabs-01.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_listtabs-01.js
@@ -18,7 +18,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_listtabs-03.js b/devtools/client/debugger/test/mochitest/browser_dbg_listtabs-03.js
index 268557b1721..902a4358a07 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_listtabs-03.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_listtabs-03.js
@@ -17,7 +17,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect(Task.async(function*(aType, aTraits) {
+  gClient.connect().then(Task.async(function*([aType, aTraits]) {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
     let tab = yield addTab(TAB1_URL);
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_multiple-windows.js b/devtools/client/debugger/test/mochitest/browser_dbg_multiple-windows.js
index 04bb6e49b6e..22cfd01e5da 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_multiple-windows.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_multiple-windows.js
@@ -20,7 +20,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_navigation.js b/devtools/client/debugger/test/mochitest/browser_dbg_navigation.js
index a4cbc49bfd0..44d6915d1dd 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_navigation.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_navigation.js
@@ -18,7 +18,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_tabactor-01.js b/devtools/client/debugger/test/mochitest/browser_dbg_tabactor-01.js
index 9fdf60942fa..9ff5cce06d8 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_tabactor-01.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_tabactor-01.js
@@ -21,7 +21,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/browser_dbg_tabactor-02.js b/devtools/client/debugger/test/mochitest/browser_dbg_tabactor-02.js
index 429e813742b..9c85eeedb2c 100644
--- a/devtools/client/debugger/test/mochitest/browser_dbg_tabactor-02.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg_tabactor-02.js
@@ -21,7 +21,7 @@ function test() {
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect((aType, aTraits) => {
+  gClient.connect().then(([aType, aTraits]) => {
     is(aType, "browser",
       "Root actor should identify itself as a browser.");
 
diff --git a/devtools/client/debugger/test/mochitest/head.js b/devtools/client/debugger/test/mochitest/head.js
index 8bdd0de1497..fec0673be91 100644
--- a/devtools/client/debugger/test/mochitest/head.js
+++ b/devtools/client/debugger/test/mochitest/head.js
@@ -564,9 +564,7 @@ AddonDebugger.prototype = {
     let transport = DebuggerServer.connectPipe();
     this.client = new DebuggerClient(transport);
 
-    let connected = promise.defer();
-    this.client.connect(connected.resolve);
-    yield connected.promise;
+    yield this.client.connect();
 
     let addonActor = yield getAddonActorForUrl(this.client, aUrl);
 
@@ -1005,11 +1003,7 @@ function generateMouseClickInTab(tab, path) {
 
 function connect(client) {
   info("Connecting client.");
-  return new Promise(function (resolve) {
-    client.connect(function () {
-      resolve();
-    });
-  });
+  return client.connect();
 }
 
 function close(client) {
diff --git a/devtools/client/framework/connect/connect.js b/devtools/client/framework/connect/connect.js
index 1825050f512..e7aa340cd09 100644
--- a/devtools/client/framework/connect/connect.js
+++ b/devtools/client/framework/connect/connect.js
@@ -74,20 +74,14 @@ var submit = Task.async(function*() {
   gClient = new DebuggerClient(transport);
   let delay = Services.prefs.getIntPref("devtools.debugger.remote-timeout");
   gConnectionTimeout = setTimeout(handleConnectionTimeout, delay);
-  let response = yield clientConnect();
+  let response = yield gClient.connect();
   yield onConnectionReady(...response);
 });
 
-function clientConnect() {
-  let deferred = promise.defer();
-  gClient.connect((...args) => deferred.resolve(args));
-  return deferred.promise;
-}
-
 /**
  * Connection is ready. List actors and build buttons.
  */
-var onConnectionReady = Task.async(function*(aType, aTraits) {
+var onConnectionReady = Task.async(function*([aType, aTraits]) {
   clearTimeout(gConnectionTimeout);
 
   let response = yield gClient.listAddons();
diff --git a/devtools/client/framework/gDevTools.jsm b/devtools/client/framework/gDevTools.jsm
index 8014d65930f..361e24b11d5 100644
--- a/devtools/client/framework/gDevTools.jsm
+++ b/devtools/client/framework/gDevTools.jsm
@@ -731,7 +731,7 @@ var gDevToolsBrowser = {
     let client = new DebuggerClient(transport);
 
     let deferred = promise.defer();
-    client.connect(() => {
+    client.connect().then(() => {
       client.mainRoot.listProcesses(response => {
         // Do nothing if there is only one process, the parent process.
         let contentProcesses = response.processes.filter(p => (!p.parent));
diff --git a/devtools/client/framework/target.js b/devtools/client/framework/target.js
index ae42ebc5441..604068cd540 100644
--- a/devtools/client/framework/target.js
+++ b/devtools/client/framework/target.js
@@ -414,12 +414,12 @@ TabTarget.prototype = {
     };
 
     if (this.isLocalTab) {
-      this._client.connect(() => {
-        this._client.getTab({ tab: this.tab }).then(response => {
+      this._client.connect()
+        .then(() => this._client.getTab({ tab: this.tab }))
+        .then(response => {
           this._form = response.tab;
           attachTab();
         });
-      });
     } else if (this.isTabActor) {
       // In the remote debugging case, the protocol connection will have been
       // already initialized in the connection screen code.
diff --git a/devtools/client/framework/test/browser_toolbox_tool_remote_reopen.js b/devtools/client/framework/test/browser_toolbox_tool_remote_reopen.js
index eff76dd3333..14d585779de 100644
--- a/devtools/client/framework/test/browser_toolbox_tool_remote_reopen.js
+++ b/devtools/client/framework/test/browser_toolbox_tool_remote_reopen.js
@@ -73,11 +73,7 @@ function getClient() {
   let transport = DebuggerServer.connectPipe();
   let client = new DebuggerClient(transport);
 
-  client.connect(() => {
-    deferred.resolve(client);
-  });
-
-  return deferred.promise;
+  return client.connect().then(() => client);
 }
 
 function getTarget(client) {
diff --git a/devtools/client/framework/test/browser_two_tabs.js b/devtools/client/framework/test/browser_two_tabs.js
index 9b9f609fbbc..41dcc721cb5 100644
--- a/devtools/client/framework/test/browser_two_tabs.js
+++ b/devtools/client/framework/test/browser_two_tabs.js
@@ -44,15 +44,15 @@ function openTabs() {
 function connect() {
   // Connect to debugger server to fetch the two tab actors
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(() => {
-    gClient.listTabs(response => {
+  gClient.connect()
+    .then(() => gClient.listTabs())
+    .then(response => {
       // Fetch the tab actors for each tab
       gTabActor1 = response.tabs.filter(a => a.url === TAB_URL_1)[0];
       gTabActor2 = response.tabs.filter(a => a.url === TAB_URL_2)[0];
 
       checkGetTab();
     });
-  });
 }
 
 function checkGetTab() {
diff --git a/devtools/client/framework/test/head.js b/devtools/client/framework/test/head.js
index a54275e85d4..977268197cc 100644
--- a/devtools/client/framework/test/head.js
+++ b/devtools/client/framework/test/head.js
@@ -29,11 +29,11 @@ function getChromeActors(callback)
   DebuggerServer.allowChromeProcess = true;
 
   let client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(() => {
-    client.getProcess().then(response => {
+  client.connect()
+    .then(() => client.getProcess())
+    .then(response => {
       callback(client, response.form);
     });
-  });
 
   SimpleTest.registerCleanupFunction(() => {
     DebuggerServer.destroy();
diff --git a/devtools/client/framework/toolbox-process-window.js b/devtools/client/framework/toolbox-process-window.js
index 21649ab79be..f50f9095dae 100644
--- a/devtools/client/framework/toolbox-process-window.js
+++ b/devtools/client/framework/toolbox-process-window.js
@@ -33,7 +33,7 @@ var connect = Task.async(function*() {
     port: Prefs.chromeDebuggingPort
   });
   gClient = new DebuggerClient(transport);
-  gClient.connect(() => {
+  gClient.connect().then(() => {
     let addonID = getParameterByName("addonID");
 
     if (addonID) {
diff --git a/devtools/client/scratchpad/scratchpad.js b/devtools/client/scratchpad/scratchpad.js
index ead372e941b..4dff1db53a3 100644
--- a/devtools/client/scratchpad/scratchpad.js
+++ b/devtools/client/scratchpad/scratchpad.js
@@ -2193,8 +2193,6 @@ ScratchpadWindow.prototype = Heritage.extend(ScratchpadTab.prototype, {
    */
   _attach: function SW__attach()
   {
-    let deferred = promise.defer();
-
     if (!DebuggerServer.initialized) {
       DebuggerServer.init();
       DebuggerServer.addBrowserActors();
@@ -2202,19 +2200,11 @@ ScratchpadWindow.prototype = Heritage.extend(ScratchpadTab.prototype, {
     DebuggerServer.allowChromeProcess = true;
 
     let client = new DebuggerClient(DebuggerServer.connectPipe());
-    client.connect(() => {
-      client.getProcess().then(aResponse => {
-        if (aResponse.error) {
-          reportError("listTabs", aResponse);
-          deferred.reject(aResponse);
-        }
-        else {
-          deferred.resolve({ form: aResponse.form, client: client });
-        }
+    return client.connect()
+      .then(() => client.getProcess())
+      .then(aResponse => {
+        return { form: aResponse.form, client: client };
       });
-    });
-
-    return deferred.promise;
   }
 });
 
diff --git a/devtools/client/shared/test/test-actor-registry.js b/devtools/client/shared/test/test-actor-registry.js
index bd551d358bf..e0ead0c13d5 100644
--- a/devtools/client/shared/test/test-actor-registry.js
+++ b/devtools/client/shared/test/test-actor-registry.js
@@ -78,9 +78,7 @@ exports.getTestActorWithoutToolbox = Task.async(function* (tab) {
   }
   let client = new DebuggerClient(DebuggerServer.connectPipe());
 
-  let deferred = promise.defer();
-  client.connect(deferred.resolve);
-  yield deferred.promise;
+  yield client.connect();
 
   // We also need to make sure the test actor is registered on the server.
   yield registerTestActor(client);
diff --git a/devtools/client/webconsole/hudservice.js b/devtools/client/webconsole/hudservice.js
index d3c3fa4ab21..c4373f0ede1 100644
--- a/devtools/client/webconsole/hudservice.js
+++ b/devtools/client/webconsole/hudservice.js
@@ -192,15 +192,13 @@ HUD_SERVICE.prototype =
       DebuggerServer.allowChromeProcess = true;
 
       let client = new DebuggerClient(DebuggerServer.connectPipe());
-      client.connect(() => {
-        client.getProcess().then(aResponse => {
+      return client.connect()
+        .then(() => client.getProcess())
+        .then(aResponse => {
           // Set chrome:false in order to attach to the target
           // (i.e. send an `attach` request to the chrome actor)
-          deferred.resolve({ form: aResponse.form, client: client, chrome: false });
-        }, deferred.reject);
-      });
-
-      return deferred.promise;
+          return { form: aResponse.form, client: client, chrome: false };
+        });
     }
 
     let target;
diff --git a/devtools/server/tests/browser/browser_register_actor.js b/devtools/server/tests/browser/browser_register_actor.js
index 0c30dc30941..567f0896b5b 100644
--- a/devtools/server/tests/browser/browser_register_actor.js
+++ b/devtools/server/tests/browser/browser_register_actor.js
@@ -11,8 +11,9 @@ function test() {
   }
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function onConnect() {
-    gClient.listTabs(function onListTabs(aResponse) {
+  gClient.connect()
+    .then(() => gClient.listTabs())
+    .then(aResponse => {
 
       var options = {
         prefix: "helloActor",
@@ -41,7 +42,6 @@ function test() {
         });
       });
     });
-  });
 }
 
 function checkActorState(helloActor, callback) {
diff --git a/devtools/server/tests/browser/head.js b/devtools/server/tests/browser/head.js
index 81a5249f687..db8130026aa 100644
--- a/devtools/server/tests/browser/head.js
+++ b/devtools/server/tests/browser/head.js
@@ -81,13 +81,11 @@ function initDebuggerServer() {
  * connected.
  */
 function connectDebuggerClient(client) {
-  return new Promise(resolve => {
-    client.connect(() => {
-      client.listTabs(tabs => {
-        resolve(tabs.tabs[tabs.selected]);
-      });
+  return client.connect()
+    .then(() => client.listTabs())
+    .then(tabs => {
+      return tabs.tabs[tabs.selected];
     });
-  });
 }
 
 /**
diff --git a/devtools/server/tests/mochitest/director-helpers.js b/devtools/server/tests/mochitest/director-helpers.js
index 968ff2ea3ca..effee775a12 100644
--- a/devtools/server/tests/mochitest/director-helpers.js
+++ b/devtools/server/tests/mochitest/director-helpers.js
@@ -13,8 +13,6 @@ SimpleTest.registerCleanupFunction(function() {
   Services.prefs.clearUserPref("dom.mozBrowserFramesEnabled");
 });
 
-const {promiseInvoke} = require("devtools/shared/async-utils");
-
 const { DirectorRegistry,
         DirectorRegistryFront } = require("devtools/server/actors/director-registry");
 
@@ -30,7 +28,7 @@ function* newConnectedDebuggerClient(opts) {
   var transport = DebuggerServer.connectPipe();
   var client = new DebuggerClient(transport);
 
-  yield promiseInvoke(client, client.connect);
+  yield client.connect();
 
   var root = yield client.listTabs();
 
diff --git a/devtools/server/tests/mochitest/inspector-helpers.js b/devtools/server/tests/mochitest/inspector-helpers.js
index 3b966622cb2..37f938d2cf4 100644
--- a/devtools/server/tests/mochitest/inspector-helpers.js
+++ b/devtools/server/tests/mochitest/inspector-helpers.js
@@ -58,7 +58,7 @@ function attachURL(url, callback) {
   window.addEventListener("message", function loadListener(event) {
     if (event.data === "ready") {
       client = new DebuggerClient(DebuggerServer.connectPipe());
-      client.connect((applicationType, traits) => {
+      client.connect().then(([applicationType, traits]) => {
         client.listTabs(response => {
           for (let tab of response.tabs) {
             if (tab.url === url) {
diff --git a/devtools/server/tests/mochitest/memory-helpers.js b/devtools/server/tests/mochitest/memory-helpers.js
index 938dbca8604..df8203aa070 100644
--- a/devtools/server/tests/mochitest/memory-helpers.js
+++ b/devtools/server/tests/mochitest/memory-helpers.js
@@ -22,26 +22,14 @@ function startServerAndGetSelectedTabMemory() {
   DebuggerServer.addBrowserActors();
   var client = new DebuggerClient(DebuggerServer.connectPipe());
 
-  return new Promise((resolve, reject) => {
-    client.connect(response => {
-      if (response.error) {
-        reject(new Error(response.error + ": " + response.message));
-        return;
-      }
+  return client.connect()
+    .then(() => client.listTabs())
+    .then(response => {
+      var form = response.tabs[response.selected];
+      var memory = MemoryFront(client, form, response);
 
-      client.listTabs(response => {
-        if (response.error) {
-          reject(new Error(response.error + ": " + response.message));
-          return;
-        }
-
-        var form = response.tabs[response.selected];
-        var memory = MemoryFront(client, form, response);
-
-        resolve({ memory, client });
-      });
+      return { memory, client };
     });
-  });
 }
 
 function destroyServerAndFinish(client) {
diff --git a/devtools/server/tests/mochitest/memprof-helpers.js b/devtools/server/tests/mochitest/memprof-helpers.js
index e1f8fefa11e..33187e0bbe4 100644
--- a/devtools/server/tests/mochitest/memprof-helpers.js
+++ b/devtools/server/tests/mochitest/memprof-helpers.js
@@ -23,26 +23,14 @@ function startServerAndGetSelectedTabMemprof() {
   DebuggerServer.addBrowserActors();
   var client = new DebuggerClient(DebuggerServer.connectPipe());
 
-  return new Promise((resolve, reject) => {
-    client.connect(response => {
-      if (response.error) {
-        reject(new Error(response.error + ": " + response.message));
-        return;
-      }
+  return client.connect()
+    .then(() => client.listTabs())
+    .then(response => {
+      var form = response.tabs[response.selected];
+      var memprof = MemprofFront(client, form);
 
-      client.listTabs(response => {
-        if (response.error) {
-          reject(new Error(response.error + ": " + response.message));
-          return;
-        }
-
-        var form = response.tabs[response.selected];
-        var memprof = MemprofFront(client, form);
-
-        resolve({ memprof, client });
-      });
+      return { memprof, client };
     });
-  });
 }
 
 function destroyServerAndFinish(client) {
diff --git a/devtools/server/tests/mochitest/test_device.html b/devtools/server/tests/mochitest/test_device.html
index 96535563234..3722d5ba6eb 100644
--- a/devtools/server/tests/mochitest/test_device.html
+++ b/devtools/server/tests/mochitest/test_device.html
@@ -34,7 +34,7 @@ window.onload = function() {
   }
 
   var client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     client.listTabs(function onListTabs(aResponse) {
       var d = getDeviceFront(client, aResponse);
 
diff --git a/devtools/server/tests/mochitest/test_framerate_01.html b/devtools/server/tests/mochitest/test_framerate_01.html
index ec45708de4e..1323e3a20ec 100644
--- a/devtools/server/tests/mochitest/test_framerate_01.html
+++ b/devtools/server/tests/mochitest/test_framerate_01.html
@@ -75,7 +75,7 @@ window.onload = function() {
   }
 
   var client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     client.listTabs(function onListTabs(aResponse) {
       var form = aResponse.tabs[aResponse.selected];
       var front = FramerateFront(client, form);
diff --git a/devtools/server/tests/mochitest/test_framerate_02.html b/devtools/server/tests/mochitest/test_framerate_02.html
index 3588b7ff88f..c9ea9ce5415 100644
--- a/devtools/server/tests/mochitest/test_framerate_02.html
+++ b/devtools/server/tests/mochitest/test_framerate_02.html
@@ -75,7 +75,7 @@ window.onload = function() {
   }
 
   var client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     client.listTabs(function onListTabs(aResponse) {
       var form = aResponse.tabs[aResponse.selected];
       var front = FramerateFront(client, form);
diff --git a/devtools/server/tests/mochitest/test_framerate_03.html b/devtools/server/tests/mochitest/test_framerate_03.html
index 867c5478d52..5c51fa2a39d 100644
--- a/devtools/server/tests/mochitest/test_framerate_03.html
+++ b/devtools/server/tests/mochitest/test_framerate_03.html
@@ -43,7 +43,7 @@ window.onload = function() {
   }
 
   var client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     client.listTabs(function onListTabs(aResponse) {
       var form = aResponse.tabs[aResponse.selected];
       var front = FramerateFront(client, form);
diff --git a/devtools/server/tests/mochitest/test_framerate_05.html b/devtools/server/tests/mochitest/test_framerate_05.html
index 0a28b6801ca..afa7f146137 100644
--- a/devtools/server/tests/mochitest/test_framerate_05.html
+++ b/devtools/server/tests/mochitest/test_framerate_05.html
@@ -38,7 +38,7 @@ window.onload = function() {
   DebuggerServer.addBrowserActors();
 
   var client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     client.listTabs(function onListTabs(aResponse) {
       var form = aResponse.tabs[aResponse.selected];
       var front = FramerateFront(client, form);
diff --git a/devtools/server/tests/mochitest/test_getProcess.html b/devtools/server/tests/mochitest/test_getProcess.html
index 62d0e6d705e..130cda88a35 100644
--- a/devtools/server/tests/mochitest/test_getProcess.html
+++ b/devtools/server/tests/mochitest/test_getProcess.html
@@ -52,7 +52,7 @@ function runTests() {
     // Fake a first connection to the content process
     let transport = DebuggerServer.connectPipe();
     client = new DebuggerClient(transport);
-    client.connect(listProcess);
+    client.connect().then(listProcess);
   }
 
   function listProcess() {
diff --git a/devtools/server/tests/mochitest/test_preference.html b/devtools/server/tests/mochitest/test_preference.html
index cf42bd794ff..cdc78e10bb5 100644
--- a/devtools/server/tests/mochitest/test_preference.html
+++ b/devtools/server/tests/mochitest/test_preference.html
@@ -31,7 +31,7 @@ function runTests() {
   DebuggerServer.addBrowserActors();
 
   var client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     client.listTabs(function onListTabs(aResponse) {
       var p = getPreferenceFront(client, aResponse);
 
diff --git a/devtools/server/tests/mochitest/test_settings.html b/devtools/server/tests/mochitest/test_settings.html
index 1e2d891d416..39479d45dd4 100644
--- a/devtools/server/tests/mochitest/test_settings.html
+++ b/devtools/server/tests/mochitest/test_settings.html
@@ -35,7 +35,7 @@ function runTests() {
   DebuggerServer.addBrowserActors();
 
   var client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     client.listTabs(function onListTabs(aResponse) {
       var s = getSettingsFront(client, aResponse);
 
diff --git a/devtools/server/tests/unit/head_dbg.js b/devtools/server/tests/unit/head_dbg.js
index e07439951a5..66ff795fa21 100644
--- a/devtools/server/tests/unit/head_dbg.js
+++ b/devtools/server/tests/unit/head_dbg.js
@@ -130,11 +130,7 @@ function createTestGlobal(name) {
 
 function connect(client) {
   dump("Connecting client.\n");
-  return new Promise(function (resolve) {
-    client.connect(function () {
-      resolve();
-    });
-  });
+  return client.connect();
 }
 
 function close(client) {
@@ -423,11 +419,11 @@ function get_chrome_actors(callback)
   DebuggerServer.allowChromeProcess = true;
 
   let client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(() => {
-    client.getProcess().then(response => {
+  client.connect()
+    .then(() => client.getProcess())
+    .then(response => {
       callback(client, response.form);
     });
-  });
 }
 
 function getChromeActors(client, server = DebuggerServer) {
diff --git a/devtools/server/tests/unit/test_actor-registry-actor.js b/devtools/server/tests/unit/test_actor-registry-actor.js
index 7c39683e2a3..f46ebf8514d 100644
--- a/devtools/server/tests/unit/test_actor-registry-actor.js
+++ b/devtools/server/tests/unit/test_actor-registry-actor.js
@@ -19,7 +19,7 @@ function run_test()
   initTestDebuggerServer();
   DebuggerServer.addBrowserActors();
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(getRegistry);
+  gClient.connect().then(getRegistry);
   do_test_pending();
 }
 
diff --git a/devtools/server/tests/unit/test_add_actors.js b/devtools/server/tests/unit/test_add_actors.js
index d210076e9ea..bed40177aff 100644
--- a/devtools/server/tests/unit/test_add_actors.js
+++ b/devtools/server/tests/unit/test_add_actors.js
@@ -35,12 +35,12 @@ function run_test()
 function init()
 {
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function onConnect() {
-    gClient.listTabs(function onListTabs(aResponse) {
+  gClient.connect()
+    .then(() => gClient.listTabs())
+    .then(aResponse => {
       gActors = aResponse;
       run_next_test();
     });
-  });
 }
 
 function test_pre_init_global_actor()
diff --git a/devtools/server/tests/unit/test_attach.js b/devtools/server/tests/unit/test_attach.js
index 11ea6406ba9..f1bb1053119 100644
--- a/devtools/server/tests/unit/test_attach.js
+++ b/devtools/server/tests/unit/test_attach.js
@@ -12,7 +12,7 @@ function run_test()
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect(function(aType, aTraits) {
+  gClient.connect().then(function([aType, aTraits]) {
     attachTestTab(gClient, "test-1", function(aReply, aTabClient) {
       test_attach(aTabClient);
     });
diff --git a/devtools/server/tests/unit/test_blackboxing-01.js b/devtools/server/tests/unit/test_blackboxing-01.js
index 3465f23934b..332444f57a5 100644
--- a/devtools/server/tests/unit/test_blackboxing-01.js
+++ b/devtools/server/tests/unit/test_blackboxing-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-black-box");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-black-box", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       testBlackBox();
diff --git a/devtools/server/tests/unit/test_blackboxing-02.js b/devtools/server/tests/unit/test_blackboxing-02.js
index a62daf33d83..ab125092ab9 100644
--- a/devtools/server/tests/unit/test_blackboxing-02.js
+++ b/devtools/server/tests/unit/test_blackboxing-02.js
@@ -16,7 +16,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-black-box");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-black-box", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_black_box();
diff --git a/devtools/server/tests/unit/test_blackboxing-03.js b/devtools/server/tests/unit/test_blackboxing-03.js
index 86487153880..ce866bf2588 100644
--- a/devtools/server/tests/unit/test_blackboxing-03.js
+++ b/devtools/server/tests/unit/test_blackboxing-03.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-black-box");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-black-box", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_black_box();
diff --git a/devtools/server/tests/unit/test_blackboxing-04.js b/devtools/server/tests/unit/test_blackboxing-04.js
index c2004359c32..611de9afffa 100644
--- a/devtools/server/tests/unit/test_blackboxing-04.js
+++ b/devtools/server/tests/unit/test_blackboxing-04.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-black-box");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-black-box", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_black_box();
diff --git a/devtools/server/tests/unit/test_blackboxing-05.js b/devtools/server/tests/unit/test_blackboxing-05.js
index 15aac272624..862e14d5742 100644
--- a/devtools/server/tests/unit/test_blackboxing-05.js
+++ b/devtools/server/tests/unit/test_blackboxing-05.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-black-box");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-black-box", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       // XXX: We have to do an executeSoon so that the error isn't caught and
diff --git a/devtools/server/tests/unit/test_blackboxing-06.js b/devtools/server/tests/unit/test_blackboxing-06.js
index 13760967664..23238c20f7e 100644
--- a/devtools/server/tests/unit/test_blackboxing-06.js
+++ b/devtools/server/tests/unit/test_blackboxing-06.js
@@ -16,7 +16,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-black-box");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-black-box", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
 
diff --git a/devtools/server/tests/unit/test_blackboxing-07.js b/devtools/server/tests/unit/test_blackboxing-07.js
index 24a634db474..ebd541a0265 100644
--- a/devtools/server/tests/unit/test_blackboxing-07.js
+++ b/devtools/server/tests/unit/test_blackboxing-07.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-black-box");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-black-box", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       testBlackBox();
diff --git a/devtools/server/tests/unit/test_breakpoint-01.js b/devtools/server/tests/unit/test_breakpoint-01.js
index e75cbdd7ea8..efdc20e3562 100644
--- a/devtools/server/tests/unit/test_breakpoint-01.js
+++ b/devtools/server/tests/unit/test_breakpoint-01.js
@@ -23,7 +23,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-02.js b/devtools/server/tests/unit/test_breakpoint-02.js
index 0bc6a2f40d3..7ec8e63960b 100644
--- a/devtools/server/tests/unit/test_breakpoint-02.js
+++ b/devtools/server/tests/unit/test_breakpoint-02.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_breakpoint_running();
diff --git a/devtools/server/tests/unit/test_breakpoint-03.js b/devtools/server/tests/unit/test_breakpoint-03.js
index 5db5d499460..0c472bb0744 100644
--- a/devtools/server/tests/unit/test_breakpoint-03.js
+++ b/devtools/server/tests/unit/test_breakpoint-03.js
@@ -26,7 +26,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient,
                            "test-stack",
                            function (aResponse, aTabClient, aThreadClient) {
diff --git a/devtools/server/tests/unit/test_breakpoint-04.js b/devtools/server/tests/unit/test_breakpoint-04.js
index ee3366c2e21..ed86a99bc5a 100644
--- a/devtools/server/tests/unit/test_breakpoint-04.js
+++ b/devtools/server/tests/unit/test_breakpoint-04.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_child_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-05.js b/devtools/server/tests/unit/test_breakpoint-05.js
index cf5e630e20f..a059978f660 100644
--- a/devtools/server/tests/unit/test_breakpoint-05.js
+++ b/devtools/server/tests/unit/test_breakpoint-05.js
@@ -25,7 +25,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_child_skip_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-06.js b/devtools/server/tests/unit/test_breakpoint-06.js
index c39675d719a..5c1e2ec5e5d 100644
--- a/devtools/server/tests/unit/test_breakpoint-06.js
+++ b/devtools/server/tests/unit/test_breakpoint-06.js
@@ -25,7 +25,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_nested_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-07.js b/devtools/server/tests/unit/test_breakpoint-07.js
index 12766ac0659..6731d88cfe5 100644
--- a/devtools/server/tests/unit/test_breakpoint-07.js
+++ b/devtools/server/tests/unit/test_breakpoint-07.js
@@ -25,7 +25,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_second_child_skip_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-08.js b/devtools/server/tests/unit/test_breakpoint-08.js
index a1bca9c0c26..e54af0dd29f 100644
--- a/devtools/server/tests/unit/test_breakpoint-08.js
+++ b/devtools/server/tests/unit/test_breakpoint-08.js
@@ -25,7 +25,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_child_skip_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-09.js b/devtools/server/tests/unit/test_breakpoint-09.js
index 5735af904e7..fee611da521 100644
--- a/devtools/server/tests/unit/test_breakpoint-09.js
+++ b/devtools/server/tests/unit/test_breakpoint-09.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_remove_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-10.js b/devtools/server/tests/unit/test_breakpoint-10.js
index 2de01c60992..65fd90018d1 100644
--- a/devtools/server/tests/unit/test_breakpoint-10.js
+++ b/devtools/server/tests/unit/test_breakpoint-10.js
@@ -25,7 +25,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_child_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-11.js b/devtools/server/tests/unit/test_breakpoint-11.js
index ef8eb8c4be8..74e580f5f22 100644
--- a/devtools/server/tests/unit/test_breakpoint-11.js
+++ b/devtools/server/tests/unit/test_breakpoint-11.js
@@ -25,7 +25,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_child_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-12.js b/devtools/server/tests/unit/test_breakpoint-12.js
index a184e5aeb6a..62063155af4 100644
--- a/devtools/server/tests/unit/test_breakpoint-12.js
+++ b/devtools/server/tests/unit/test_breakpoint-12.js
@@ -29,7 +29,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_child_skip_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-13.js b/devtools/server/tests/unit/test_breakpoint-13.js
index 307b058a411..db5deaec36e 100644
--- a/devtools/server/tests/unit/test_breakpoint-13.js
+++ b/devtools/server/tests/unit/test_breakpoint-13.js
@@ -25,7 +25,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-14.js b/devtools/server/tests/unit/test_breakpoint-14.js
index 163b357bb37..bd288e5ca7d 100644
--- a/devtools/server/tests/unit/test_breakpoint-14.js
+++ b/devtools/server/tests/unit/test_breakpoint-14.js
@@ -25,7 +25,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_breakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-15.js b/devtools/server/tests/unit/test_breakpoint-15.js
index 1e9935a2a26..6a3ab7c6f55 100644
--- a/devtools/server/tests/unit/test_breakpoint-15.js
+++ b/devtools/server/tests/unit/test_breakpoint-15.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       testSameBreakpoint();
diff --git a/devtools/server/tests/unit/test_breakpoint-16.js b/devtools/server/tests/unit/test_breakpoint-16.js
index 8aaba8f6121..10408c40d0e 100644
--- a/devtools/server/tests/unit/test_breakpoint-16.js
+++ b/devtools/server/tests/unit/test_breakpoint-16.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-breakpoints", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient,
                            "test-breakpoints",
                            function (aResponse, aTabClient, aThreadClient) {
diff --git a/devtools/server/tests/unit/test_breakpoint-17.js b/devtools/server/tests/unit/test_breakpoint-17.js
index 0f501f4625f..bd093a2fc12 100644
--- a/devtools/server/tests/unit/test_breakpoint-17.js
+++ b/devtools/server/tests/unit/test_breakpoint-17.js
@@ -23,7 +23,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-breakpoints", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-breakpoints", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_breakpoints_columns();
diff --git a/devtools/server/tests/unit/test_breakpoint-18.js b/devtools/server/tests/unit/test_breakpoint-18.js
index 81909bc0375..74414adeaeb 100644
--- a/devtools/server/tests/unit/test_breakpoint-18.js
+++ b/devtools/server/tests/unit/test_breakpoint-18.js
@@ -26,7 +26,7 @@ function run_test_with_server(aServer, aCallback)
   gDebuggee = addTestGlobal("test-breakpoints", aServer);
   gDebuggee.console = { log: x => void x };
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient,
                            "test-breakpoints",
                            function (aResponse, aTabClient, aThreadClient) {
diff --git a/devtools/server/tests/unit/test_breakpoint-19.js b/devtools/server/tests/unit/test_breakpoint-19.js
index b869592a73f..68784bfb9f8 100644
--- a/devtools/server/tests/unit/test_breakpoint-19.js
+++ b/devtools/server/tests/unit/test_breakpoint-19.js
@@ -26,7 +26,7 @@ function run_test_with_server(aServer, aCallback)
   gDebuggee = addTestGlobal("test-breakpoints", aServer);
   gDebuggee.console = { log: x => void x };
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient,
                            "test-breakpoints",
                            function (aResponse, aTabClient, aThreadClient) {
diff --git a/devtools/server/tests/unit/test_breakpoint-20.js b/devtools/server/tests/unit/test_breakpoint-20.js
index 20e8d24949d..fb673f825e3 100644
--- a/devtools/server/tests/unit/test_breakpoint-20.js
+++ b/devtools/server/tests/unit/test_breakpoint-20.js
@@ -16,7 +16,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-breakpoints");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestThread(gClient, "test-breakpoints", testBreakpoint);
   });
   do_test_pending();
diff --git a/devtools/server/tests/unit/test_breakpoint-21.js b/devtools/server/tests/unit/test_breakpoint-21.js
index 9ca9cf1e945..8b7dd84c473 100644
--- a/devtools/server/tests/unit/test_breakpoint-21.js
+++ b/devtools/server/tests/unit/test_breakpoint-21.js
@@ -26,7 +26,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-breakpoints", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient,
                            "test-breakpoints",
                            function (aResponse, aTabClient, aThreadClient) {
diff --git a/devtools/server/tests/unit/test_client_close.js b/devtools/server/tests/unit/test_client_close.js
index 9909c4ce839..14fa66efad0 100644
--- a/devtools/server/tests/unit/test_client_close.js
+++ b/devtools/server/tests/unit/test_client_close.js
@@ -12,7 +12,7 @@ function run_test()
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect(function(aType, aTraits) {
+  gClient.connect().then(function(aType, aTraits) {
     attachTestTab(gClient, "test-1", function(aReply, aTabClient) {
       test_close(transport);
     });
diff --git a/devtools/server/tests/unit/test_client_request.js b/devtools/server/tests/unit/test_client_request.js
index 9bd4f337964..bad82906106 100644
--- a/devtools/server/tests/unit/test_client_request.js
+++ b/devtools/server/tests/unit/test_client_request.js
@@ -45,12 +45,12 @@ function run_test()
 function init()
 {
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function onConnect() {
-    gClient.listTabs(function onListTabs(aResponse) {
+  gClient.connect()
+    .then(() => gClient.listTabs())
+    .then(aResponse => {
       gActorId = aResponse.test;
       run_next_test();
     });
-  });
 }
 
 function checkStack(expectedName) {
diff --git a/devtools/server/tests/unit/test_conditional_breakpoint-01.js b/devtools/server/tests/unit/test_conditional_breakpoint-01.js
index 3f68d14aaf5..4661bb0c4c2 100644
--- a/devtools/server/tests/unit/test_conditional_breakpoint-01.js
+++ b/devtools/server/tests/unit/test_conditional_breakpoint-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-conditional-breakpoint");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-conditional-breakpoint", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_breakpoint();
diff --git a/devtools/server/tests/unit/test_conditional_breakpoint-02.js b/devtools/server/tests/unit/test_conditional_breakpoint-02.js
index 266750488b8..30f511d351b 100644
--- a/devtools/server/tests/unit/test_conditional_breakpoint-02.js
+++ b/devtools/server/tests/unit/test_conditional_breakpoint-02.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-conditional-breakpoint");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-conditional-breakpoint", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_breakpoint();
diff --git a/devtools/server/tests/unit/test_conditional_breakpoint-03.js b/devtools/server/tests/unit/test_conditional_breakpoint-03.js
index 50e911d54ae..d9cf13e005d 100644
--- a/devtools/server/tests/unit/test_conditional_breakpoint-03.js
+++ b/devtools/server/tests/unit/test_conditional_breakpoint-03.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-conditional-breakpoint");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-conditional-breakpoint", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_breakpoint();
diff --git a/devtools/server/tests/unit/test_dbgclient_debuggerstatement.js b/devtools/server/tests/unit/test_dbgclient_debuggerstatement.js
index 35a2163f1b8..208d3d07c01 100644
--- a/devtools/server/tests/unit/test_dbgclient_debuggerstatement.js
+++ b/devtools/server/tests/unit/test_dbgclient_debuggerstatement.js
@@ -13,7 +13,7 @@ function run_test()
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect(function(aType, aTraits) {
+  gClient.connect().then(function([aType, aTraits]) {
     attachTestTab(gClient, "test-1", function(aReply, aTabClient) {
       gTabClient = aTabClient;
       test_threadAttach(aReply.threadActor);
diff --git a/devtools/server/tests/unit/test_eval-01.js b/devtools/server/tests/unit/test_eval-01.js
index 03bbcfbf569..21e08c30cfe 100644
--- a/devtools/server/tests/unit/test_eval-01.js
+++ b/devtools/server/tests/unit/test_eval-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_eval();
diff --git a/devtools/server/tests/unit/test_eval-02.js b/devtools/server/tests/unit/test_eval-02.js
index 6dcb607e785..9dddb3bd380 100644
--- a/devtools/server/tests/unit/test_eval-02.js
+++ b/devtools/server/tests/unit/test_eval-02.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_throw_eval();
diff --git a/devtools/server/tests/unit/test_eval-03.js b/devtools/server/tests/unit/test_eval-03.js
index 867fe56169a..c335937f009 100644
--- a/devtools/server/tests/unit/test_eval-03.js
+++ b/devtools/server/tests/unit/test_eval-03.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_syntax_error_eval();
diff --git a/devtools/server/tests/unit/test_eval-04.js b/devtools/server/tests/unit/test_eval-04.js
index 302b591df77..534f505a1a6 100644
--- a/devtools/server/tests/unit/test_eval-04.js
+++ b/devtools/server/tests/unit/test_eval-04.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_syntax_error_eval();
diff --git a/devtools/server/tests/unit/test_eval-05.js b/devtools/server/tests/unit/test_eval-05.js
index 3f779b3233f..26d0afd64c0 100644
--- a/devtools/server/tests/unit/test_eval-05.js
+++ b/devtools/server/tests/unit/test_eval-05.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_syntax_error_eval();
diff --git a/devtools/server/tests/unit/test_eventlooplag_actor.js b/devtools/server/tests/unit/test_eventlooplag_actor.js
index a97c1d321d5..4dd531879b5 100644
--- a/devtools/server/tests/unit/test_eventlooplag_actor.js
+++ b/devtools/server/tests/unit/test_eventlooplag_actor.js
@@ -23,7 +23,7 @@ function run_test()
   let client = new DebuggerClient(DebuggerServer.connectPipe());
 
   // Start tracking event loop lags.
-  client.connect(function () {
+  client.connect().then(function () {
     client.listTabs(function(resp) {
       front = new EventLoopLagFront(client, resp);
       front.start().then(success => {
diff --git a/devtools/server/tests/unit/test_forwardingprefix.js b/devtools/server/tests/unit/test_forwardingprefix.js
index ab289799bdb..4b3d7429ab6 100644
--- a/devtools/server/tests/unit/test_forwardingprefix.js
+++ b/devtools/server/tests/unit/test_forwardingprefix.js
@@ -52,7 +52,7 @@ function createMainConnection()
 {
   ({ conn: gMainConnection, transport: gMainTransport } = newConnection());
   gClient = new DebuggerClient(gMainTransport);
-  gClient.connect((aType, aTraits) => run_next_test());
+  gClient.connect().then(([aType, aTraits]) => run_next_test());
 }
 
 /*
diff --git a/devtools/server/tests/unit/test_frameactor-01.js b/devtools/server/tests/unit/test_frameactor-01.js
index 52125d7cb0d..e8f7ed56c74 100644
--- a/devtools/server/tests/unit/test_frameactor-01.js
+++ b/devtools/server/tests/unit/test_frameactor-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_frameactor-02.js b/devtools/server/tests/unit/test_frameactor-02.js
index 2c6c01ccea6..5825df9a51c 100644
--- a/devtools/server/tests/unit/test_frameactor-02.js
+++ b/devtools/server/tests/unit/test_frameactor-02.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_frameactor-03.js b/devtools/server/tests/unit/test_frameactor-03.js
index b7c08d31a05..68e8c4572c8 100644
--- a/devtools/server/tests/unit/test_frameactor-03.js
+++ b/devtools/server/tests/unit/test_frameactor-03.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_frameactor-04.js b/devtools/server/tests/unit/test_frameactor-04.js
index 96c2285cbb2..d58e9ff1bb8 100644
--- a/devtools/server/tests/unit/test_frameactor-04.js
+++ b/devtools/server/tests/unit/test_frameactor-04.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_frameactor-05.js b/devtools/server/tests/unit/test_frameactor-05.js
index 409edb77f70..0ba1e84cc02 100644
--- a/devtools/server/tests/unit/test_frameactor-05.js
+++ b/devtools/server/tests/unit/test_frameactor-05.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_framearguments-01.js b/devtools/server/tests/unit/test_framearguments-01.js
index 3c5613ef113..785f618040a 100644
--- a/devtools/server/tests/unit/test_framearguments-01.js
+++ b/devtools/server/tests/unit/test_framearguments-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_framebindings-01.js b/devtools/server/tests/unit/test_framebindings-01.js
index 405f95c145c..ecf8d62fa24 100644
--- a/devtools/server/tests/unit/test_framebindings-01.js
+++ b/devtools/server/tests/unit/test_framebindings-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_framebindings-02.js b/devtools/server/tests/unit/test_framebindings-02.js
index d3f8073df82..4249c77952c 100644
--- a/devtools/server/tests/unit/test_framebindings-02.js
+++ b/devtools/server/tests/unit/test_framebindings-02.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_framebindings-03.js b/devtools/server/tests/unit/test_framebindings-03.js
index eed8649aa09..91138081b37 100644
--- a/devtools/server/tests/unit/test_framebindings-03.js
+++ b/devtools/server/tests/unit/test_framebindings-03.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_framebindings-04.js b/devtools/server/tests/unit/test_framebindings-04.js
index b2d71ffe507..ea6d3c27fff 100644
--- a/devtools/server/tests/unit/test_framebindings-04.js
+++ b/devtools/server/tests/unit/test_framebindings-04.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_framebindings-05.js b/devtools/server/tests/unit/test_framebindings-05.js
index 32d670750b8..060bdf7aaf8 100644
--- a/devtools/server/tests/unit/test_framebindings-05.js
+++ b/devtools/server/tests/unit/test_framebindings-05.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_framebindings-06.js b/devtools/server/tests/unit/test_framebindings-06.js
index 2f714f9cc31..738f19cea80 100644
--- a/devtools/server/tests/unit/test_framebindings-06.js
+++ b/devtools/server/tests/unit/test_framebindings-06.js
@@ -11,7 +11,7 @@ function run_test()
   gDebuggee = addTestGlobal("test-grips");
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_banana_environment();
diff --git a/devtools/server/tests/unit/test_framebindings-07.js b/devtools/server/tests/unit/test_framebindings-07.js
index 47c7e69c800..a01b96e70c9 100644
--- a/devtools/server/tests/unit/test_framebindings-07.js
+++ b/devtools/server/tests/unit/test_framebindings-07.js
@@ -12,7 +12,7 @@ function run_test()
   gDebuggee = addTestGlobal("test-bindings");
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-bindings", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_banana_environment();
diff --git a/devtools/server/tests/unit/test_frameclient-01.js b/devtools/server/tests/unit/test_frameclient-01.js
index b75e7eb20c7..56019dd4ff4 100644
--- a/devtools/server/tests/unit/test_frameclient-01.js
+++ b/devtools/server/tests/unit/test_frameclient-01.js
@@ -10,7 +10,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_frameclient-02.js b/devtools/server/tests/unit/test_frameclient-02.js
index 7e12abbc861..a66deedff47 100644
--- a/devtools/server/tests/unit/test_frameclient-02.js
+++ b/devtools/server/tests/unit/test_frameclient-02.js
@@ -10,7 +10,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_functiongrips-01.js b/devtools/server/tests/unit/test_functiongrips-01.js
index 8c3ba605c89..3fef2ff07fa 100644
--- a/devtools/server/tests/unit/test_functiongrips-01.js
+++ b/devtools/server/tests/unit/test_functiongrips-01.js
@@ -14,7 +14,7 @@ function run_test()
   }.toString());
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_named_function();
diff --git a/devtools/server/tests/unit/test_get-executable-lines-source-map.js b/devtools/server/tests/unit/test_get-executable-lines-source-map.js
index b32e69aab85..bc30e299115 100644
--- a/devtools/server/tests/unit/test_get-executable-lines-source-map.js
+++ b/devtools/server/tests/unit/test_get-executable-lines-source-map.js
@@ -16,7 +16,7 @@ function run_test() {
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-get-executable-lines");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function _onConnect() {
+  gClient.connect().then(function _onConnect() {
     attachTestTabAndResume(
       gClient,
       "test-get-executable-lines",
diff --git a/devtools/server/tests/unit/test_get-executable-lines.js b/devtools/server/tests/unit/test_get-executable-lines.js
index 2228fa5259f..447eab3e587 100644
--- a/devtools/server/tests/unit/test_get-executable-lines.js
+++ b/devtools/server/tests/unit/test_get-executable-lines.js
@@ -16,7 +16,7 @@ function run_test() {
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-get-executable-lines");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function _onConnect() {
+  gClient.connect().then(function _onConnect() {
     attachTestTabAndResume(
       gClient,
       "test-get-executable-lines",
diff --git a/devtools/server/tests/unit/test_ignore_caught_exceptions.js b/devtools/server/tests/unit/test_ignore_caught_exceptions.js
index 09cdb8070be..c438b95d157 100644
--- a/devtools/server/tests/unit/test_ignore_caught_exceptions.js
+++ b/devtools/server/tests/unit/test_ignore_caught_exceptions.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_interrupt.js b/devtools/server/tests/unit/test_interrupt.js
index 01d8cfb4835..7c0021d21ec 100644
--- a/devtools/server/tests/unit/test_interrupt.js
+++ b/devtools/server/tests/unit/test_interrupt.js
@@ -12,7 +12,7 @@ function run_test()
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect(function(aType, aTraits) {
+  gClient.connect().then(function(aType, aTraits) {
     attachTestTab(gClient, "test-1", test_attach);
   });
   do_test_pending();
diff --git a/devtools/server/tests/unit/test_listsources-01.js b/devtools/server/tests/unit/test_listsources-01.js
index 1d9b58f92a2..231e6a1e4fa 100644
--- a/devtools/server/tests/unit/test_listsources-01.js
+++ b/devtools/server/tests/unit/test_listsources-01.js
@@ -24,7 +24,7 @@ function run_test()
       return request.call(this, aRequest, aOnResponse);
     };
   }(gClient.request));
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_listsources();
diff --git a/devtools/server/tests/unit/test_listsources-02.js b/devtools/server/tests/unit/test_listsources-02.js
index 09ac39d843c..190a5e31bc9 100644
--- a/devtools/server/tests/unit/test_listsources-02.js
+++ b/devtools/server/tests/unit/test_listsources-02.js
@@ -24,7 +24,7 @@ function run_test()
       return request.call(this, aRequest, aOnResponse);
     };
   }(gClient.request));
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_listing_zero_sources();
diff --git a/devtools/server/tests/unit/test_listsources-03.js b/devtools/server/tests/unit/test_listsources-03.js
index a0d401dc151..72ebb5e1c28 100644
--- a/devtools/server/tests/unit/test_listsources-03.js
+++ b/devtools/server/tests/unit/test_listsources-03.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-sources");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-sources", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_listsources();
diff --git a/devtools/server/tests/unit/test_longstringgrips-01.js b/devtools/server/tests/unit/test_longstringgrips-01.js
index a488590d5c6..e2321833456 100644
--- a/devtools/server/tests/unit/test_longstringgrips-01.js
+++ b/devtools/server/tests/unit/test_longstringgrips-01.js
@@ -14,7 +14,7 @@ function run_test()
   }.toString());
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_longstring_grip();
diff --git a/devtools/server/tests/unit/test_longstringgrips-02.js b/devtools/server/tests/unit/test_longstringgrips-02.js
index 62262d3b509..5fed8389c9d 100644
--- a/devtools/server/tests/unit/test_longstringgrips-02.js
+++ b/devtools/server/tests/unit/test_longstringgrips-02.js
@@ -14,7 +14,7 @@ function run_test()
   }.toString());
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(
       gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
         gThreadClient = aThreadClient;
diff --git a/devtools/server/tests/unit/test_memory_footprint.js b/devtools/server/tests/unit/test_memory_footprint.js
index abc1291b7cb..f7c5c677635 100644
--- a/devtools/server/tests/unit/test_memory_footprint.js
+++ b/devtools/server/tests/unit/test_memory_footprint.js
@@ -39,7 +39,7 @@ function add_browser_actors() {
 
 function connect_client() {
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function onConnect() {
+  gClient.connect().then(function onConnect() {
     check_footprint("DebuggerClient.connect()", 2000);
   });
 }
diff --git a/devtools/server/tests/unit/test_nesting-01.js b/devtools/server/tests/unit/test_nesting-01.js
index dcfb0fe6322..e515f051ee8 100644
--- a/devtools/server/tests/unit/test_nesting-01.js
+++ b/devtools/server/tests/unit/test_nesting-01.js
@@ -12,7 +12,7 @@ function run_test() {
   initTestDebuggerServer();
   let gDebuggee = addTestGlobal("test-nesting");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-nesting", function (aResponse, aTabClient, aThreadClient) {
       // Reach over the protocol connection and get a reference to the thread actor.
       gThreadActor = aThreadClient._transport._serverConnection.getActor(aThreadClient._actor);
diff --git a/devtools/server/tests/unit/test_nesting-02.js b/devtools/server/tests/unit/test_nesting-02.js
index e217c2611b8..928331be569 100644
--- a/devtools/server/tests/unit/test_nesting-02.js
+++ b/devtools/server/tests/unit/test_nesting-02.js
@@ -12,7 +12,7 @@ function run_test() {
   initTestDebuggerServer();
   let gDebuggee = addTestGlobal("test-nesting");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-nesting", function (aResponse, aTabClient, aThreadClient) {
       // Reach over the protocol connection and get a reference to the thread
       // actor.
diff --git a/devtools/server/tests/unit/test_new_source-01.js b/devtools/server/tests/unit/test_new_source-01.js
index 533f30ce0ba..f4a430f2d60 100644
--- a/devtools/server/tests/unit/test_new_source-01.js
+++ b/devtools/server/tests/unit/test_new_source-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_new_source();
diff --git a/devtools/server/tests/unit/test_objectgrips-01.js b/devtools/server/tests/unit/test_objectgrips-01.js
index f90238a38cc..62bbccb0ca7 100644
--- a/devtools/server/tests/unit/test_objectgrips-01.js
+++ b/devtools/server/tests/unit/test_objectgrips-01.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-02.js b/devtools/server/tests/unit/test_objectgrips-02.js
index 0b7b12f9180..fc3da8cd62e 100644
--- a/devtools/server/tests/unit/test_objectgrips-02.js
+++ b/devtools/server/tests/unit/test_objectgrips-02.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-03.js b/devtools/server/tests/unit/test_objectgrips-03.js
index 6cebb7fc2fa..ea2b8ba2c57 100644
--- a/devtools/server/tests/unit/test_objectgrips-03.js
+++ b/devtools/server/tests/unit/test_objectgrips-03.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-04.js b/devtools/server/tests/unit/test_objectgrips-04.js
index 9e295f80f6e..aa89a03dba1 100644
--- a/devtools/server/tests/unit/test_objectgrips-04.js
+++ b/devtools/server/tests/unit/test_objectgrips-04.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-05.js b/devtools/server/tests/unit/test_objectgrips-05.js
index 04fde877f25..eca0a3efc19 100644
--- a/devtools/server/tests/unit/test_objectgrips-05.js
+++ b/devtools/server/tests/unit/test_objectgrips-05.js
@@ -29,7 +29,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-06.js b/devtools/server/tests/unit/test_objectgrips-06.js
index 7971f28fbd2..4bb77249e69 100644
--- a/devtools/server/tests/unit/test_objectgrips-06.js
+++ b/devtools/server/tests/unit/test_objectgrips-06.js
@@ -29,7 +29,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-07.js b/devtools/server/tests/unit/test_objectgrips-07.js
index 9ecce818ddc..7cbd6d18026 100644
--- a/devtools/server/tests/unit/test_objectgrips-07.js
+++ b/devtools/server/tests/unit/test_objectgrips-07.js
@@ -29,7 +29,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-08.js b/devtools/server/tests/unit/test_objectgrips-08.js
index 591278d6671..640acd909e2 100644
--- a/devtools/server/tests/unit/test_objectgrips-08.js
+++ b/devtools/server/tests/unit/test_objectgrips-08.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-09.js b/devtools/server/tests/unit/test_objectgrips-09.js
index c87726c688d..0392e4dfc9f 100644
--- a/devtools/server/tests/unit/test_objectgrips-09.js
+++ b/devtools/server/tests/unit/test_objectgrips-09.js
@@ -28,7 +28,7 @@ function run_test_with_server(aServer, aCallback)
   }.toString());
 
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-10.js b/devtools/server/tests/unit/test_objectgrips-10.js
index 67451e3075a..d61d4598410 100644
--- a/devtools/server/tests/unit/test_objectgrips-10.js
+++ b/devtools/server/tests/unit/test_objectgrips-10.js
@@ -13,7 +13,7 @@ function run_test()
   gDebuggee = addTestGlobal("test-closures");
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-closures", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-11.js b/devtools/server/tests/unit/test_objectgrips-11.js
index 94d594577a9..a223693c7b9 100644
--- a/devtools/server/tests/unit/test_objectgrips-11.js
+++ b/devtools/server/tests/unit/test_objectgrips-11.js
@@ -16,7 +16,7 @@ function run_test()
   }.toString());
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_object_grip();
diff --git a/devtools/server/tests/unit/test_objectgrips-12.js b/devtools/server/tests/unit/test_objectgrips-12.js
index fdcd9070453..e0c81523fb7 100644
--- a/devtools/server/tests/unit/test_objectgrips-12.js
+++ b/devtools/server/tests/unit/test_objectgrips-12.js
@@ -16,7 +16,7 @@ function run_test()
   }.toString());
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_display_string();
diff --git a/devtools/server/tests/unit/test_objectgrips-13.js b/devtools/server/tests/unit/test_objectgrips-13.js
index 13f650b69af..1523dd2ecc0 100644
--- a/devtools/server/tests/unit/test_objectgrips-13.js
+++ b/devtools/server/tests/unit/test_objectgrips-13.js
@@ -17,7 +17,7 @@ function run_test()
   }.toString(), gDebuggee);
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       add_pause_listener();
diff --git a/devtools/server/tests/unit/test_pause_exceptions-01.js b/devtools/server/tests/unit/test_pause_exceptions-01.js
index 0ca75e388af..92f9165587a 100644
--- a/devtools/server/tests/unit/test_pause_exceptions-01.js
+++ b/devtools/server/tests/unit/test_pause_exceptions-01.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_pause_exceptions-02.js b/devtools/server/tests/unit/test_pause_exceptions-02.js
index 54174ec08ea..bebf295f365 100644
--- a/devtools/server/tests/unit/test_pause_exceptions-02.js
+++ b/devtools/server/tests/unit/test_pause_exceptions-02.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_pauselifetime-01.js b/devtools/server/tests/unit/test_pauselifetime-01.js
index a7af929456b..3cbff5a88bb 100644
--- a/devtools/server/tests/unit/test_pauselifetime-01.js
+++ b/devtools/server/tests/unit/test_pauselifetime-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_pauselifetime-02.js b/devtools/server/tests/unit/test_pauselifetime-02.js
index bfbb18e3990..521d2082da4 100644
--- a/devtools/server/tests/unit/test_pauselifetime-02.js
+++ b/devtools/server/tests/unit/test_pauselifetime-02.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_pauselifetime-03.js b/devtools/server/tests/unit/test_pauselifetime-03.js
index 058ca42e64e..0d7a48c1de2 100644
--- a/devtools/server/tests/unit/test_pauselifetime-03.js
+++ b/devtools/server/tests/unit/test_pauselifetime-03.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_pauselifetime-04.js b/devtools/server/tests/unit/test_pauselifetime-04.js
index a9d90d0215b..f537668dbf7 100644
--- a/devtools/server/tests/unit/test_pauselifetime-04.js
+++ b/devtools/server/tests/unit/test_pauselifetime-04.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-stack");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-stack", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_pause_frame();
diff --git a/devtools/server/tests/unit/test_promise_state-01.js b/devtools/server/tests/unit/test_promise_state-01.js
index d04321d279c..6e658ae7fbc 100644
--- a/devtools/server/tests/unit/test_promise_state-01.js
+++ b/devtools/server/tests/unit/test_promise_state-01.js
@@ -11,7 +11,7 @@ function run_test()
   initTestDebuggerServer();
   const debuggee = addTestGlobal("test-promise-state");
   const client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function() {
+  client.connect().then(function() {
     attachTestTabAndResume(client, "test-promise-state", function (response, tabClient, threadClient) {
       Task.spawn(function* () {
         const packet = yield executeOnNextTickAndWaitForPause(() => evalCode(debuggee), client);
diff --git a/devtools/server/tests/unit/test_promise_state-02.js b/devtools/server/tests/unit/test_promise_state-02.js
index 1a9cb5bb42b..83b8d9ee511 100644
--- a/devtools/server/tests/unit/test_promise_state-02.js
+++ b/devtools/server/tests/unit/test_promise_state-02.js
@@ -11,7 +11,7 @@ function run_test()
   initTestDebuggerServer();
   const debuggee = addTestGlobal("test-promise-state");
   const client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function() {
+  client.connect().then(function() {
     attachTestTabAndResume(client, "test-promise-state", function (response, tabClient, threadClient) {
       Task.spawn(function* () {
         const packet = yield executeOnNextTickAndWaitForPause(() => evalCode(debuggee), client);
diff --git a/devtools/server/tests/unit/test_promise_state-03.js b/devtools/server/tests/unit/test_promise_state-03.js
index 9f686ba2d2f..615b1217a90 100644
--- a/devtools/server/tests/unit/test_promise_state-03.js
+++ b/devtools/server/tests/unit/test_promise_state-03.js
@@ -11,7 +11,7 @@ function run_test()
   initTestDebuggerServer();
   const debuggee = addTestGlobal("test-promise-state");
   const client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function() {
+  client.connect().then(function() {
     attachTestTabAndResume(client, "test-promise-state", function (response, tabClient, threadClient) {
       Task.spawn(function* () {
         const packet = yield executeOnNextTickAndWaitForPause(() => evalCode(debuggee), client);
diff --git a/devtools/server/tests/unit/test_protocol_abort.js b/devtools/server/tests/unit/test_protocol_abort.js
index 665e4f1b37e..efa959a1ff0 100644
--- a/devtools/server/tests/unit/test_protocol_abort.js
+++ b/devtools/server/tests/unit/test_protocol_abort.js
@@ -54,7 +54,7 @@ function run_test() {
   let client = new DebuggerClient(trace);
   let rootClient;
 
-  client.connect((applicationType, traits) => {
+  client.connect().then(([applicationType, traits]) => {
     rootClient = RootFront(client);
 
     rootClient.simpleReturn().then(() => {
diff --git a/devtools/server/tests/unit/test_protocol_async.js b/devtools/server/tests/unit/test_protocol_async.js
index 65c8bfb7059..44fdd4a946f 100644
--- a/devtools/server/tests/unit/test_protocol_async.js
+++ b/devtools/server/tests/unit/test_protocol_async.js
@@ -97,7 +97,7 @@ function run_test()
   let client = new DebuggerClient(trace);
   let rootClient;
 
-  client.connect((applicationType, traits) => {
+  client.connect().then([applicationType, traits]) => {
     rootClient = RootFront(client);
 
     let calls = [];
diff --git a/devtools/server/tests/unit/test_protocol_children.js b/devtools/server/tests/unit/test_protocol_children.js
index f7b072c89a2..a61c76cb574 100644
--- a/devtools/server/tests/unit/test_protocol_children.js
+++ b/devtools/server/tests/unit/test_protocol_children.js
@@ -303,7 +303,7 @@ function run_test()
 
   let trace = connectPipeTracing();
   let client = new DebuggerClient(trace);
-  client.connect((applicationType, traits) => {
+  client.connect().then(([applicationType, traits]) => {
     trace.expectReceive({"from":"<actorid>","applicationType":"xpcshell-tests","traits":[]})
     do_check_eq(applicationType, "xpcshell-tests");
 
diff --git a/devtools/server/tests/unit/test_protocol_longstring.js b/devtools/server/tests/unit/test_protocol_longstring.js
index 462154810b4..99e123cf540 100644
--- a/devtools/server/tests/unit/test_protocol_longstring.js
+++ b/devtools/server/tests/unit/test_protocol_longstring.js
@@ -96,7 +96,7 @@ function run_test()
   }
 
 
-  client.connect((applicationType, traits) => {
+  client.connect().then(([applicationType, traits]) => {
     rootClient = RootFront(client);
 
     // Root actor has no children yet.
diff --git a/devtools/server/tests/unit/test_protocol_simple.js b/devtools/server/tests/unit/test_protocol_simple.js
index e6f734aeac7..05a6f3d1732 100644
--- a/devtools/server/tests/unit/test_protocol_simple.js
+++ b/devtools/server/tests/unit/test_protocol_simple.js
@@ -180,7 +180,7 @@ function run_test()
   let client = new DebuggerClient(trace);
   let rootClient;
 
-  client.connect((applicationType, traits) => {
+  client.connect().then(([applicationType, traits]) => {
     trace.expectReceive({"from":"<actorid>","applicationType":"xpcshell-tests","traits":[]});
     do_check_eq(applicationType, "xpcshell-tests");
 
diff --git a/devtools/server/tests/unit/test_protocol_stack.js b/devtools/server/tests/unit/test_protocol_stack.js
index c4fab033871..0328e514f62 100644
--- a/devtools/server/tests/unit/test_protocol_stack.js
+++ b/devtools/server/tests/unit/test_protocol_stack.js
@@ -63,7 +63,7 @@ function run_test() {
   let client = new DebuggerClient(trace);
   let rootClient;
 
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     rootClient = RootFront(client);
 
     rootClient.simpleReturn().then(() => {
diff --git a/devtools/server/tests/unit/test_reattach-thread.js b/devtools/server/tests/unit/test_reattach-thread.js
index e83100a28bf..e7ec07f6ba2 100644
--- a/devtools/server/tests/unit/test_reattach-thread.js
+++ b/devtools/server/tests/unit/test_reattach-thread.js
@@ -15,7 +15,7 @@ function run_test()
 
   let transport = DebuggerServer.connectPipe();
   gClient = new DebuggerClient(transport);
-  gClient.connect(() => {
+  gClient.connect().then(() => {
     attachTestTab(gClient, "test-reattach", (aReply, aTabClient) => {
       gTabClient = aTabClient;
       test_attach();
diff --git a/devtools/server/tests/unit/test_registerClient.js b/devtools/server/tests/unit/test_registerClient.js
index 1fb3a425c59..a5d961c15a0 100644
--- a/devtools/server/tests/unit/test_registerClient.js
+++ b/devtools/server/tests/unit/test_registerClient.js
@@ -65,13 +65,13 @@ function run_test()
 function init()
 {
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function onConnect() {
-    gClient.listTabs(function onListTabs(aResponse) {
+  gClient.connect()
+    .then(() => gClient.listTabs())
+    .then(aResponse => {
       gActors = aResponse;
       gTestClient = new TestClient(gClient, aResponse);
       run_next_test();
     });
-  });
 }
 
 function test_client_events()
diff --git a/devtools/server/tests/unit/test_register_actor.js b/devtools/server/tests/unit/test_register_actor.js
index 7a9f0170180..3f326270196 100644
--- a/devtools/server/tests/unit/test_register_actor.js
+++ b/devtools/server/tests/unit/test_register_actor.js
@@ -74,7 +74,7 @@ function test_lazy_api() {
   do_check_false(isActorInstanciated);
 
   let client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function onConnect() {
+  client.connect().then(function onConnect() {
     client.listTabs(onListTabs);
   });
   function onListTabs(aResponse) {
diff --git a/devtools/server/tests/unit/test_requestTypes.js b/devtools/server/tests/unit/test_requestTypes.js
index 014c9920638..5695a6571aa 100644
--- a/devtools/server/tests/unit/test_requestTypes.js
+++ b/devtools/server/tests/unit/test_requestTypes.js
@@ -28,7 +28,7 @@ function run_test()
   DebuggerServer.addBrowserActors();
 
   var client = new DebuggerClient(DebuggerServer.connectPipe());
-  client.connect(function() {
+  client.connect().then(function() {
     test_requestTypes_request(client);
   });
 
diff --git a/devtools/server/tests/unit/test_source-01.js b/devtools/server/tests/unit/test_source-01.js
index 2d605cda777..044e30c34d9 100644
--- a/devtools/server/tests/unit/test_source-01.js
+++ b/devtools/server/tests/unit/test_source-01.js
@@ -24,7 +24,7 @@ function run_test()
   );
 
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_source();
diff --git a/devtools/server/tests/unit/test_sourcemaps-01.js b/devtools/server/tests/unit/test_sourcemaps-01.js
index 930bcd803a7..1ce6c734842 100644
--- a/devtools/server/tests/unit/test_sourcemaps-01.js
+++ b/devtools/server/tests/unit/test_sourcemaps-01.js
@@ -16,7 +16,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_source_map();
diff --git a/devtools/server/tests/unit/test_sourcemaps-02.js b/devtools/server/tests/unit/test_sourcemaps-02.js
index d8faca53311..94604263270 100644
--- a/devtools/server/tests/unit/test_sourcemaps-02.js
+++ b/devtools/server/tests/unit/test_sourcemaps-02.js
@@ -16,7 +16,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_source_map();
diff --git a/devtools/server/tests/unit/test_sourcemaps-03.js b/devtools/server/tests/unit/test_sourcemaps-03.js
index ba0f538859e..a9d85391143 100644
--- a/devtools/server/tests/unit/test_sourcemaps-03.js
+++ b/devtools/server/tests/unit/test_sourcemaps-03.js
@@ -16,7 +16,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_source_map();
diff --git a/devtools/server/tests/unit/test_sourcemaps-04.js b/devtools/server/tests/unit/test_sourcemaps-04.js
index db05eee7da4..626feab5054 100644
--- a/devtools/server/tests/unit/test_sourcemaps-04.js
+++ b/devtools/server/tests/unit/test_sourcemaps-04.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_absolute_source_map();
diff --git a/devtools/server/tests/unit/test_sourcemaps-05.js b/devtools/server/tests/unit/test_sourcemaps-05.js
index 0ba5dc3158e..c80f6ef110e 100644
--- a/devtools/server/tests/unit/test_sourcemaps-05.js
+++ b/devtools/server/tests/unit/test_sourcemaps-05.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_relative_source_map();
diff --git a/devtools/server/tests/unit/test_sourcemaps-06.js b/devtools/server/tests/unit/test_sourcemaps-06.js
index eba5a862d13..ff4a394b523 100644
--- a/devtools/server/tests/unit/test_sourcemaps-06.js
+++ b/devtools/server/tests/unit/test_sourcemaps-06.js
@@ -17,7 +17,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_source_content();
diff --git a/devtools/server/tests/unit/test_sourcemaps-07.js b/devtools/server/tests/unit/test_sourcemaps-07.js
index 82a5ef3724e..a81e17eac2e 100644
--- a/devtools/server/tests/unit/test_sourcemaps-07.js
+++ b/devtools/server/tests/unit/test_sourcemaps-07.js
@@ -16,7 +16,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_cached_original_sources();
diff --git a/devtools/server/tests/unit/test_sourcemaps-08.js b/devtools/server/tests/unit/test_sourcemaps-08.js
index 693b790fd8c..17a35a8f335 100644
--- a/devtools/server/tests/unit/test_sourcemaps-08.js
+++ b/devtools/server/tests/unit/test_sourcemaps-08.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_source_maps();
diff --git a/devtools/server/tests/unit/test_sourcemaps-09.js b/devtools/server/tests/unit/test_sourcemaps-09.js
index 16d08c16b78..ee3467f51b5 100644
--- a/devtools/server/tests/unit/test_sourcemaps-09.js
+++ b/devtools/server/tests/unit/test_sourcemaps-09.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_minified();
diff --git a/devtools/server/tests/unit/test_sourcemaps-10.js b/devtools/server/tests/unit/test_sourcemaps-10.js
index 85730f21fbb..60dd032dd9a 100644
--- a/devtools/server/tests/unit/test_sourcemaps-10.js
+++ b/devtools/server/tests/unit/test_sourcemaps-10.js
@@ -15,7 +15,7 @@ function run_test() {
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       promise.resolve(define_code())
diff --git a/devtools/server/tests/unit/test_sourcemaps-11.js b/devtools/server/tests/unit/test_sourcemaps-11.js
index 40b457f8049..781a38e2123 100644
--- a/devtools/server/tests/unit/test_sourcemaps-11.js
+++ b/devtools/server/tests/unit/test_sourcemaps-11.js
@@ -15,7 +15,7 @@ function run_test() {
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       promise.resolve(define_code())
diff --git a/devtools/server/tests/unit/test_sourcemaps-12.js b/devtools/server/tests/unit/test_sourcemaps-12.js
index 465ee5b56b9..43d06f494d1 100644
--- a/devtools/server/tests/unit/test_sourcemaps-12.js
+++ b/devtools/server/tests/unit/test_sourcemaps-12.js
@@ -16,7 +16,7 @@ function run_test() {
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       define_code();
diff --git a/devtools/server/tests/unit/test_sourcemaps-13.js b/devtools/server/tests/unit/test_sourcemaps-13.js
index 45aabeec886..8d9dd4c2d92 100644
--- a/devtools/server/tests/unit/test_sourcemaps-13.js
+++ b/devtools/server/tests/unit/test_sourcemaps-13.js
@@ -17,7 +17,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-source-map");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-source-map", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       gTabClient = aTabClient;
diff --git a/devtools/server/tests/unit/test_sourcemaps-16.js b/devtools/server/tests/unit/test_sourcemaps-16.js
index 708e4a254c2..8876a698069 100644
--- a/devtools/server/tests/unit/test_sourcemaps-16.js
+++ b/devtools/server/tests/unit/test_sourcemaps-16.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-sourcemaps");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestThread(gClient, "test-sourcemaps", testSourcemap);
   });
   do_test_pending();
diff --git a/devtools/server/tests/unit/test_stepping-01.js b/devtools/server/tests/unit/test_stepping-01.js
index b292665d6dd..f9761c0b5ff 100644
--- a/devtools/server/tests/unit/test_stepping-01.js
+++ b/devtools/server/tests/unit/test_stepping-01.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_stepping();
diff --git a/devtools/server/tests/unit/test_stepping-02.js b/devtools/server/tests/unit/test_stepping-02.js
index c313808aaeb..74232972ee0 100644
--- a/devtools/server/tests/unit/test_stepping-02.js
+++ b/devtools/server/tests/unit/test_stepping-02.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_stepping();
diff --git a/devtools/server/tests/unit/test_stepping-03.js b/devtools/server/tests/unit/test_stepping-03.js
index 6bb3ce1a40b..a17f90d9c99 100644
--- a/devtools/server/tests/unit/test_stepping-03.js
+++ b/devtools/server/tests/unit/test_stepping-03.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_stepping();
diff --git a/devtools/server/tests/unit/test_stepping-04.js b/devtools/server/tests/unit/test_stepping-04.js
index 96dc93cb46b..637f6d5a72d 100644
--- a/devtools/server/tests/unit/test_stepping-04.js
+++ b/devtools/server/tests/unit/test_stepping-04.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_simple_stepping();
diff --git a/devtools/server/tests/unit/test_stepping-05.js b/devtools/server/tests/unit/test_stepping-05.js
index 08a846e1a0c..3128e899900 100644
--- a/devtools/server/tests/unit/test_stepping-05.js
+++ b/devtools/server/tests/unit/test_stepping-05.js
@@ -26,7 +26,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_stepping_last();
diff --git a/devtools/server/tests/unit/test_stepping-06.js b/devtools/server/tests/unit/test_stepping-06.js
index e2c58bcae85..6f31392947e 100644
--- a/devtools/server/tests/unit/test_stepping-06.js
+++ b/devtools/server/tests/unit/test_stepping-06.js
@@ -24,7 +24,7 @@ function run_test_with_server(aServer, aCallback)
   initTestDebuggerServer(aServer);
   gDebuggee = addTestGlobal("test-stack", aServer);
   gClient = new DebuggerClient(aServer.connectPipe());
-  gClient.connect(function () {
+  gClient.connect().then(function () {
     attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       // XXX: We have to do an executeSoon so that the error isn't caught and
diff --git a/devtools/server/tests/unit/test_symbols-01.js b/devtools/server/tests/unit/test_symbols-01.js
index 0976a998a73..d850779b065 100644
--- a/devtools/server/tests/unit/test_symbols-01.js
+++ b/devtools/server/tests/unit/test_symbols-01.js
@@ -12,7 +12,7 @@ function run_test() {
   const debuggee = addTestGlobal("test-symbols");
   const client = new DebuggerClient(DebuggerServer.connectPipe());
 
-  client.connect(function() {
+  client.connect().then(function() {
     attachTestTabAndResume(client, "test-symbols", function(response, tabClient, threadClient) {
       add_task(testSymbols.bind(null, client, debuggee));
       run_next_test();
diff --git a/devtools/server/tests/unit/test_symbols-02.js b/devtools/server/tests/unit/test_symbols-02.js
index 95753d6ddbb..61e8616ae5f 100644
--- a/devtools/server/tests/unit/test_symbols-02.js
+++ b/devtools/server/tests/unit/test_symbols-02.js
@@ -12,7 +12,7 @@ function run_test() {
   const debuggee = addTestGlobal("test-symbols");
   const client = new DebuggerClient(DebuggerServer.connectPipe());
 
-  client.connect(function() {
+  client.connect().then(function() {
     attachTestTabAndResume(client, "test-symbols", function(response, tabClient, threadClient) {
       add_task(testSymbols.bind(null, client, debuggee));
       run_next_test();
diff --git a/devtools/server/tests/unit/test_threadlifetime-01.js b/devtools/server/tests/unit/test_threadlifetime-01.js
index 3ebd93c8272..2a530dedbb3 100644
--- a/devtools/server/tests/unit/test_threadlifetime-01.js
+++ b/devtools/server/tests/unit/test_threadlifetime-01.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-grips");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_thread_lifetime();
diff --git a/devtools/server/tests/unit/test_threadlifetime-02.js b/devtools/server/tests/unit/test_threadlifetime-02.js
index b56143cdeff..1308e3b1a2a 100644
--- a/devtools/server/tests/unit/test_threadlifetime-02.js
+++ b/devtools/server/tests/unit/test_threadlifetime-02.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-grips");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_thread_lifetime();
diff --git a/devtools/server/tests/unit/test_threadlifetime-03.js b/devtools/server/tests/unit/test_threadlifetime-03.js
index 60fa595f02c..1ccf837946c 100644
--- a/devtools/server/tests/unit/test_threadlifetime-03.js
+++ b/devtools/server/tests/unit/test_threadlifetime-03.js
@@ -14,7 +14,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-grips");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_thread_lifetime();
diff --git a/devtools/server/tests/unit/test_threadlifetime-04.js b/devtools/server/tests/unit/test_threadlifetime-04.js
index 38cd38dd6ea..ad3e00f7b68 100644
--- a/devtools/server/tests/unit/test_threadlifetime-04.js
+++ b/devtools/server/tests/unit/test_threadlifetime-04.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-grips");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function (aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_thread_lifetime();
diff --git a/devtools/server/tests/unit/test_threadlifetime-05.js b/devtools/server/tests/unit/test_threadlifetime-05.js
index 7795f010061..eda9ebc7640 100644
--- a/devtools/server/tests/unit/test_threadlifetime-05.js
+++ b/devtools/server/tests/unit/test_threadlifetime-05.js
@@ -16,7 +16,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-grips");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_thread_lifetime();
diff --git a/devtools/server/tests/unit/test_threadlifetime-06.js b/devtools/server/tests/unit/test_threadlifetime-06.js
index b71a48dc748..d6967b8d6db 100644
--- a/devtools/server/tests/unit/test_threadlifetime-06.js
+++ b/devtools/server/tests/unit/test_threadlifetime-06.js
@@ -15,7 +15,7 @@ function run_test()
   initTestDebuggerServer();
   gDebuggee = addTestGlobal("test-grips");
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function() {
+  gClient.connect().then(function() {
     attachTestTabAndResume(gClient, "test-grips", function(aResponse, aTabClient, aThreadClient) {
       gThreadClient = aThreadClient;
       test_thread_lifetime();
diff --git a/devtools/server/tests/unit/test_xpcshell_debugging.js b/devtools/server/tests/unit/test_xpcshell_debugging.js
index 602639a89e4..201419777d5 100644
--- a/devtools/server/tests/unit/test_xpcshell_debugging.js
+++ b/devtools/server/tests/unit/test_xpcshell_debugging.js
@@ -12,7 +12,7 @@ function run_test() {
   let DebuggerServer = _setupDebuggerServer([testFile.path], () => testResumed = true);
   let transport = DebuggerServer.connectPipe();
   let client = new DebuggerClient(transport);
-  client.connect(() => {
+  client.connect().then(() => {
     // Even though we have no tabs, listTabs gives us the chromeDebugger.
     client.getProcess().then(response => {
       let actor = response.form.actor;
diff --git a/devtools/shared/apps/tests/debugger-protocol-helper.js b/devtools/shared/apps/tests/debugger-protocol-helper.js
index 2240dd7521c..2865c18aef8 100644
--- a/devtools/shared/apps/tests/debugger-protocol-helper.js
+++ b/devtools/shared/apps/tests/debugger-protocol-helper.js
@@ -49,13 +49,13 @@ function connect(onDone) {
 function startClient(transport, onDone) {
   // Setup client and actor used in all tests
   gClient = new DebuggerClient(transport);
-  gClient.connect(function onConnect() {
-    gClient.listTabs(function onListTabs(aResponse) {
+  gClient.connect()
+    .then(() => gClient.listTabs())
+    .then(aResponse => {
       gActor = aResponse.webappsActor;
       if (gActor)
         webappActorRequest({type: "watchApps"}, onDone);
     });
-  });
 
   gClient.addListener("appInstall", function (aState, aType, aPacket) {
     sendAsyncMessage("installed-event", { manifestURL: aType.manifestURL });
diff --git a/devtools/shared/apps/tests/unit/head_apps.js b/devtools/shared/apps/tests/unit/head_apps.js
index f24cc8bd0d5..5a72d1ed908 100644
--- a/devtools/shared/apps/tests/unit/head_apps.js
+++ b/devtools/shared/apps/tests/unit/head_apps.js
@@ -26,13 +26,13 @@ function connect(onDone) {
 
   // Setup client and actor used in all tests
   gClient = new DebuggerClient(DebuggerServer.connectPipe());
-  gClient.connect(function onConnect() {
-    gClient.listTabs(function onListTabs(aResponse) {
+  gClient.connect()
+    .then(() => gClient.listTabs())
+    .then(aResponse => {
       gActor = aResponse.webappsActor;
       gActorFront = new AppActorFront(gClient, aResponse);
       onDone();
     });
-  });
 }
 
 function webappActorRequest(request, onResponse) {
diff --git a/devtools/shared/client/connection-manager.js b/devtools/shared/client/connection-manager.js
index c8880f8573f..ae982ab7ec7 100644
--- a/devtools/shared/client/connection-manager.js
+++ b/devtools/shared/client/connection-manager.js
@@ -316,7 +316,7 @@ Connection.prototype = {
       }
       this._client = new DebuggerClient(transport);
       this._client.addOneTimeListener("closed", this._onDisconnected);
-      this._client.connect(this._onConnected);
+      this._client.connect().then(this._onConnected);
     }, e => {
       // If we're continuously trying to connect, we expect the connection to be
       // rejected a couple times, so don't log these.
diff --git a/devtools/shared/client/main.js b/devtools/shared/client/main.js
index 425b67ced47..bad301d3805 100644
--- a/devtools/shared/client/main.js
+++ b/devtools/shared/client/main.js
@@ -335,8 +335,15 @@ DebuggerClient.prototype = {
    * @param aOnConnected function
    *        If specified, will be called when the greeting packet is
    *        received from the debugging server.
+   *
+   * @return Promise
+   *         Resolves once connected with an array whose first element
+   *         is the application type, by default "browser", and the second
+   *         element is the traits object (help figure out the features
+   *         and behaviors of the server we connect to. See RootActor).
    */
   connect: function (aOnConnected) {
+    let deferred = promise.defer();
     this.emit("connect");
 
     // Also emit the event on the |DebuggerClient| object (not on the instance),
@@ -348,9 +355,11 @@ DebuggerClient.prototype = {
       if (aOnConnected) {
         aOnConnected(aApplicationType, aTraits);
       }
+      deferred.resolve([aApplicationType, aTraits]);
     });
 
     this._transport.ready();
+    return deferred.promise;
   },
 
   /**
diff --git a/devtools/shared/security/tests/unit/test_oob_cert_auth.js b/devtools/shared/security/tests/unit/test_oob_cert_auth.js
index fed389cbc1b..77a8caacbda 100644
--- a/devtools/shared/security/tests/unit/test_oob_cert_auth.js
+++ b/devtools/shared/security/tests/unit/test_oob_cert_auth.js
@@ -16,11 +16,9 @@ function run_test() {
 }
 
 function connectClient(client) {
-  let deferred = promise.defer();
-  client.connect(() => {
-    client.listTabs(deferred.resolve);
+  return client.connect(() => {
+    return client.listTabs();
   });
-  return deferred.promise;
 }
 
 add_task(function*() {
diff --git a/devtools/shared/transport/tests/unit/test_bulk_error.js b/devtools/shared/transport/tests/unit/test_bulk_error.js
index 5b41c7c0349..212ba1be336 100644
--- a/devtools/shared/transport/tests/unit/test_bulk_error.js
+++ b/devtools/shared/transport/tests/unit/test_bulk_error.js
@@ -47,21 +47,18 @@ function add_test_bulk_actor() {
 /*** Tests ***/
 
 var test_string_error = Task.async(function*(transportFactory, onReady) {
-  let deferred = promise.defer();
   let transport = yield transportFactory();
 
   let client = new DebuggerClient(transport);
-  client.connect((app, traits) => {
-    do_check_eq(traits.bulk, true);
-    client.listTabs(response => {
-      deferred.resolve(onReady(client, response).then(() => {
-        client.close();
-        transport.close();
-      }));
+  return client.connect().then(([app, traits]) => {
+      do_check_eq(traits.bulk, true);
+      return client.listTabs();
+    }).then(response => {
+      return onReady(client, response);
+    }).then(() => {
+      client.close();
+      transport.close();
     });
-  });
-
-  return deferred.promise;
 });
 
 /*** Reply Types ***/
diff --git a/devtools/shared/transport/tests/unit/test_client_server_bulk.js b/devtools/shared/transport/tests/unit/test_client_server_bulk.js
index d570cb772fc..6fe0aa41a99 100644
--- a/devtools/shared/transport/tests/unit/test_client_server_bulk.js
+++ b/devtools/shared/transport/tests/unit/test_client_server_bulk.js
@@ -144,7 +144,7 @@ var test_bulk_request_cs = Task.async(function*(transportFactory, actorType, rep
   let transport = yield transportFactory();
 
   let client = new DebuggerClient(transport);
-  client.connect((app, traits) => {
+  client.connect().then(([app, traits]) => {
     do_check_eq(traits.bulk, true);
     client.listTabs(clientDeferred.resolve);
   });
diff --git a/devtools/shared/transport/tests/unit/test_no_bulk.js b/devtools/shared/transport/tests/unit/test_no_bulk.js
index bdc89b732f5..bdf0c20f0d5 100644
--- a/devtools/shared/transport/tests/unit/test_no_bulk.js
+++ b/devtools/shared/transport/tests/unit/test_no_bulk.js
@@ -26,7 +26,7 @@ var test_bulk_send_error = Task.async(function*(transportFactory) {
   let transport = yield transportFactory();
 
   let client = new DebuggerClient(transport);
-  client.connect((app, traits) => {
+  return client.connect().then(([app, traits]) => {
     do_check_false(traits.bulk);
 
     try {
@@ -36,8 +36,5 @@ var test_bulk_send_error = Task.async(function*(transportFactory) {
       do_check_true(true);
     }
 
-    deferred.resolve();
   });
-
-  return deferred.promise;
 });
diff --git a/devtools/shared/webconsole/test/common.js b/devtools/shared/webconsole/test/common.js
index 45d84d90147..adde01b63a0 100644
--- a/devtools/shared/webconsole/test/common.js
+++ b/devtools/shared/webconsole/test/common.js
@@ -50,7 +50,7 @@ function connectToDebugger(aCallback)
   let client = new DebuggerClient(transport);
 
   let dbgState = { dbgClient: client };
-  client.connect(aCallback.bind(null, dbgState));
+  client.connect().then(response => aCallback(dbgState, response));
 }
 
 function attachConsole(aListeners, aCallback) {