diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index b1ccdbf0..a58f7fe0 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -20,7 +20,7 @@ jobs:
       yarn
     displayName: 'Install dependencies and build'
   - script: |
-      yarn test-unit
+      yarn test-unit --forbid-only
     displayName: 'Unit tests'
   - script: |
       yarn lint
@@ -38,7 +38,7 @@ jobs:
       yarn
     displayName: 'Install dependencies and build'
   - script: |
-      yarn test-unit
+      yarn test-unit --forbid-only
     displayName: 'Unit tests'
   - script: |
       yarn lint
@@ -56,7 +56,7 @@ jobs:
       yarn
     displayName: 'Install dependencies and build'
   - script: |
-      yarn test-unit
+      yarn test-unit --forbid-only
     displayName: 'Unit tests'
   - script: |
       yarn lint
@@ -80,7 +80,7 @@ jobs:
   - script: |
       yarn start &
       sleep 10
-      yarn test-api --headless
+      yarn test-api --headless --forbid-only
     displayName: 'Linux Integration tests'
 
 - job: macOS_IntegrationTests
@@ -97,7 +97,7 @@ jobs:
   - script: |
       yarn start &
       sleep 10
-      yarn test-api --headless
+      yarn test-api --headless --forbid-only
     displayName: 'MacOS Integration tests'
 
 - job: Release
diff --git a/bin/test.js b/bin/test.js
index 775ec004..3b08d4a1 100644
--- a/bin/test.js
+++ b/bin/test.js
@@ -15,15 +15,22 @@ let testFiles = [
   './out/**/*test.js'
 ];
 
-// ability to inject particular test files via
-// yarn test [testFileA testFileB ...]
+let flagArgs = [];
+
 if (process.argv.length > 2) {
-  testFiles = process.argv.slice(2);
+  const args = process.argv.slice(2);
+  flagArgs = args.filter(e => e.startsWith('--'));
+  // ability to inject particular test files via
+  // yarn test [testFileA testFileB ...]
+  files = args.filter(e => !e.startsWith('--'));
+  if (files.length) {
+    testFiles = files;
+  }
 }
 
 const run = cp.spawnSync(
   path.resolve(__dirname, '../node_modules/.bin/mocha'),
-  testFiles,
+  [...testFiles, ...flagArgs],
   {
     cwd: path.resolve(__dirname, '..'),
     env,
@@ -31,4 +38,4 @@ const run = cp.spawnSync(
   }
 );
 
-process.exit(run.status);
\ No newline at end of file
+process.exit(run.status);
diff --git a/src/Terminal.ts b/src/Terminal.ts
index 597c14cd..3e7e55ca 100644
--- a/src/Terminal.ts
+++ b/src/Terminal.ts
@@ -508,6 +508,10 @@ export class Terminal extends Disposable implements ITerminal, IDisposable, IInp
       throw new Error('Terminal requires a parent element.');
     }
 
+    if (!document.body.contains(parent)) {
+      this._logService.warn('Terminal.open was called on an element that was not attached to the DOM');
+    }
+
     this._document = this._parent.ownerDocument;
 
     // Create main element container
diff --git a/src/public/Terminal.ts b/src/public/Terminal.ts
index fe34cb36..c167bed8 100644
--- a/src/public/Terminal.ts
+++ b/src/public/Terminal.ts
@@ -56,9 +56,6 @@ export class Terminal implements ITerminalApi {
     this._core.resize(columns, rows);
   }
   public open(parent: HTMLElement): void {
-    if (!document.body.contains(parent)) {
-      throw new Error('open must be called on an element that is attached to the DOM');
-    }
     this._core.open(parent);
   }
   public attachCustomKeyEventHandler(customKeyEventHandler: (event: KeyboardEvent) => boolean): void {