Bug 787420 - Part 2/2: add test case for rolling back on error, r=philikon

dom/network/tests/marionette/manifest.ini

@@ -7,3 +7,4 @@ qemu = true
 [test_mobile_voice_state.js]
 [test_mobile_iccinfo.js]
 [test_mobile_operator_names.js]
+[test_mobile_preferred_network_type.js]

dom/network/tests/marionette/test_mobile_preferred_network_type.js

@@ -0,0 +1,68 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+MARIONETTE_TIMEOUT = 60000;
+
+const KEY = "ril.radio.preferredNetworkType";
+
+let gSettingsEnabled = SpecialPowers.getBoolPref("dom.mozSettings.enabled");
+if (!gSettingsEnabled) {
+  SpecialPowers.setBoolPref("dom.mozSettings.enabled", true);
+}
+SpecialPowers.addPermission("mobileconnection", true, document);
+SpecialPowers.addPermission("settings", true, document);
+
+let settings = window.navigator.mozSettings;
+
+function test_revert_previous_setting_on_invalid_value() {
+  log("Testing reverting to previous setting on invalid value received");
+
+  let getLock = settings.createLock();
+  let getReq = getLock.get(KEY);
+  getReq.addEventListener("success", function onGetSuccess() {
+    let originalValue = getReq.result[KEY] || "wcdma/gsm";
+
+    let setDone = false;
+    settings.addObserver(KEY, function observer(setting) {
+      // Mark if the invalid value has been set in db and wait.
+      if (setting.settingValue == obj[KEY]) {
+        setDone = true;
+        return;
+      }
+
+      // Skip any change before marking but keep it as original value.
+      if (!setDone) {
+        originalValue = setting.settingValue;
+        return;
+      }
+
+      settings.removeObserver(KEY, observer);
+      is(setting.settingValue, originalValue, "Settings reverted");
+      window.setTimeout(cleanUp, 0);
+    });
+
+    let obj = {};
+    obj[KEY] = "AnInvalidValue";
+    let setLock = settings.createLock();
+    setLock.set(obj);
+    setLock.addEventListener("error", function onSetError() {
+      ok(false, "cannot set '" + KEY + "'");
+    });
+  });
+  getReq.addEventListener("error", function onGetError() {
+    ok(false, "cannot get default value of '" + KEY + "'");
+  });
+}
+
+function cleanUp() {
+  SpecialPowers.removePermission("mobileconnection", document);
+  SpecialPowers.removePermission("settings", document);
+  SpecialPowers.clearUserPref("dom.mozSettings.enabled");
+
+  finish();
+}
+
+waitFor(test_revert_previous_setting_on_invalid_value, function () {
+  return navigator.mozMobileConnection.voice.connected;
+});
+