Add unit tests for Copilot refresh exponential backoff logic

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/test/github/copilotRefresh.test.ts

@@ -0,0 +1,79 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { default as assert } from 'assert';
+import { EventType } from '../../common/timelineEvent';
+
+describe('Copilot Refresh Logic', function () {
+	it('should detect new CopilotStarted events', function () {
+		// Test the logic for detecting new CopilotStarted events
+		const initialTimeline = [
+			{ event: EventType.Commented, id: '1' },
+			{ event: EventType.CopilotStarted, id: '2' }
+		];
+		const initialCopilotStartedEvents = initialTimeline.filter(event => event.event === EventType.CopilotStarted);
+		assert.strictEqual(initialCopilotStartedEvents.length, 1);
+
+		const newTimeline = [
+			{ event: EventType.Commented, id: '1' },
+			{ event: EventType.CopilotStarted, id: '2' },
+			{ event: EventType.CopilotStarted, id: '3' }
+		];
+		const newCopilotStartedEvents = newTimeline.filter(event => event.event === EventType.CopilotStarted);
+		assert.strictEqual(newCopilotStartedEvents.length, 2);
+		
+		// Should detect new event
+		assert.strictEqual(newCopilotStartedEvents.length > initialCopilotStartedEvents.length, true);
+	});
+
+	it('should handle empty initial timeline', function () {
+		const initialTimeline = [];
+		const initialCopilotStartedEvents = initialTimeline.filter(event => event.event === EventType.CopilotStarted);
+		assert.strictEqual(initialCopilotStartedEvents.length, 0);
+
+		const newTimeline = [
+			{ event: EventType.CopilotStarted, id: '1' }
+		];
+		const newCopilotStartedEvents = newTimeline.filter(event => event.event === EventType.CopilotStarted);
+		assert.strictEqual(newCopilotStartedEvents.length, 1);
+		
+		// Should detect new event
+		assert.strictEqual(newCopilotStartedEvents.length > initialCopilotStartedEvents.length, true);
+	});
+
+	it('should handle no new events', function () {
+		const initialTimeline = [
+			{ event: EventType.Commented, id: '1' },
+			{ event: EventType.CopilotStarted, id: '2' }
+		];
+		const initialCopilotStartedEvents = initialTimeline.filter(event => event.event === EventType.CopilotStarted);
+		assert.strictEqual(initialCopilotStartedEvents.length, 1);
+
+		const newTimeline = [
+			{ event: EventType.Commented, id: '1' },
+			{ event: EventType.CopilotStarted, id: '2' },
+			{ event: EventType.Commented, id: '3' }
+		];
+		const newCopilotStartedEvents = newTimeline.filter(event => event.event === EventType.CopilotStarted);
+		assert.strictEqual(newCopilotStartedEvents.length, 1);
+		
+		// Should not detect new event
+		assert.strictEqual(newCopilotStartedEvents.length > initialCopilotStartedEvents.length, false);
+	});
+
+	it('should verify exponential backoff delays', function () {
+		const delays = [500, 1000, 2000, 5000];
+		
+		// Verify the delays are exponential
+		assert.strictEqual(delays[0], 500);
+		assert.strictEqual(delays[1], 1000); // 2x
+		assert.strictEqual(delays[2], 2000); // 2x
+		assert.strictEqual(delays[3], 5000); // 2.5x (final value as requested)
+		
+		// Total time should be 8.5 seconds maximum
+		const totalTime = delays.reduce((sum, delay) => sum + delay, 0);
+		assert.strictEqual(totalTime, 8500);
+	});
+});