diff --git a/src/vs/workbench/api/test/browser/extHostEditorTabs.test.ts b/src/vs/workbench/api/test/browser/extHostEditorTabs.test.ts
index 09d582d9516..9929bcc0040 100644
--- a/src/vs/workbench/api/test/browser/extHostEditorTabs.test.ts
+++ b/src/vs/workbench/api/test/browser/extHostEditorTabs.test.ts
@@ -4,9 +4,10 @@
  *--------------------------------------------------------------------------------------------*/
 
 import assert = require('assert');
+import { URI } from 'vs/base/common/uri';
 import { mock } from 'vs/base/test/common/mock';
 import { IEditorTabDto, MainThreadEditorTabsShape, TabKind } from 'vs/workbench/api/common/extHost.protocol';
-import { ExtHostEditorTabs } from 'vs/workbench/api/common/extHostEditorTabs';
+import { ExtHostEditorTabs, IEditorTabGroup } from 'vs/workbench/api/common/extHostEditorTabs';
 import { SingleProxyRPCProtocol } from 'vs/workbench/api/test/common/testRPCProtocol';
 
 suite('ExtHostEditorTabs', function () {
@@ -88,4 +89,65 @@ suite('ExtHostEditorTabs', function () {
 		assert.strictEqual(first.activeTab, undefined);
 		assert.strictEqual(first.tabs.length, 0);
 	});
+
+	test('Ensure tabGroup change events fires', function () {
+		const extHostEditorTabs = new ExtHostEditorTabs(
+			SingleProxyRPCProtocol(new class extends mock<MainThreadEditorTabsShape>() {
+				// override/implement $moveTab or $closeTab
+			})
+		);
+
+		let count = 0;
+		extHostEditorTabs.onDidChangeTabGroup(() => count++);
+
+
+		assert.strictEqual(extHostEditorTabs.tabGroups.all.length, 0);
+		assert.strictEqual(extHostEditorTabs.tabGroups.activeTabGroup, undefined);
+		assert.strictEqual(count, 0);
+		extHostEditorTabs.$acceptEditorTabModel([{
+			isActive: true,
+			viewColumn: 0,
+			groupId: 12,
+			tabs: [],
+			activeTab: undefined
+		}]);
+		assert.ok(extHostEditorTabs.tabGroups.activeTabGroup);
+		const activeTabGroup: IEditorTabGroup = extHostEditorTabs.tabGroups.activeTabGroup;
+		assert.strictEqual(extHostEditorTabs.tabGroups.all.length, 1);
+		assert.strictEqual(activeTabGroup.tabs.length, 0);
+		assert.strictEqual(count, 1);
+	});
+
+	test('Ensure reference equality for activeTab and activeGroup', function () {
+		const extHostEditorTabs = new ExtHostEditorTabs(
+			SingleProxyRPCProtocol(new class extends mock<MainThreadEditorTabsShape>() {
+				// override/implement $moveTab or $closeTab
+			})
+		);
+		const tab: IEditorTabDto = {
+			isActive: true,
+			isDirty: true,
+			isPinned: true,
+			label: 'label1',
+			resource: URI.parse('file://abc/def.txt'),
+			editorId: 'default',
+			viewColumn: 0,
+			additionalResourcesAndViewIds: [],
+			kind: TabKind.Singular
+		};
+
+		extHostEditorTabs.$acceptEditorTabModel([{
+			isActive: true,
+			viewColumn: 0,
+			groupId: 12,
+			tabs: [tab],
+			activeTab: { ...tab }
+		}]);
+		assert.strictEqual(extHostEditorTabs.tabGroups.all.length, 1);
+		const [first] = extHostEditorTabs.tabGroups.all;
+		assert.ok(first.activeTab);
+		assert.strictEqual(first.tabs.indexOf(first.activeTab), 0);
+		assert.strictEqual(first.activeTab, first.tabs[0]);
+		assert.strictEqual(extHostEditorTabs.tabGroups.activeTabGroup, first);
+	});
 });