Establishing unit tests using vitest.

utils/timer.test.ts

@@ -0,0 +1,110 @@
+import { Timer } from './timer.ts';
+import * as cli from './cli.ts';
+
+describe('Timer', () => {
+  beforeEach(() => {
+    vi.spyOn(cli.log, 'debug');
+    // Mock Date.now to have predictable timestamps
+    vi.useFakeTimers();
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    vi.useRealTimers();
+  });
+
+  describe('constructor', () => {
+    it('should initialize with current timestamp', () => {
+      const mockTime = 1000000;
+      vi.setSystemTime(mockTime);
+
+      const timer = new Timer();
+      timer.checkpoint('test');
+
+      expect(cli.log.debug).toHaveBeenCalledWith(
+        expect.stringContaining('test')
+      );
+    });
+  });
+
+  describe('checkpoint', () => {
+    it('should log duration from initial timestamp on first checkpoint', () => {
+      const startTime = 1000000;
+      vi.setSystemTime(startTime);
+      const timer = new Timer();
+
+      const checkpointTime = startTime + 100;
+      vi.setSystemTime(checkpointTime);
+      timer.checkpoint('first');
+
+      expect(cli.log.debug).toHaveBeenCalledWith('» first: 100ms');
+    });
+
+    it('should log duration from last checkpoint on subsequent checkpoints', () => {
+      const startTime = 1000000;
+      vi.setSystemTime(startTime);
+      const timer = new Timer();
+
+      // First checkpoint
+      const firstCheckpointTime = startTime + 50;
+      vi.setSystemTime(firstCheckpointTime);
+      timer.checkpoint('first');
+
+      // Second checkpoint
+      const secondCheckpointTime = firstCheckpointTime + 75;
+      vi.setSystemTime(secondCheckpointTime);
+      timer.checkpoint('second');
+
+      expect(cli.log.debug).toHaveBeenCalledTimes(2);
+      expect(cli.log.debug).toHaveBeenNthCalledWith(1, '» first: 50ms');
+      expect(cli.log.debug).toHaveBeenNthCalledWith(2, '» second: 75ms');
+    });
+
+    it('should handle multiple checkpoints correctly', () => {
+      const startTime = 1000000;
+      vi.setSystemTime(startTime);
+      const timer = new Timer();
+
+      // First checkpoint
+      vi.setSystemTime(startTime + 10);
+      timer.checkpoint('step1');
+
+      // Second checkpoint
+      vi.setSystemTime(startTime + 25);
+      timer.checkpoint('step2');
+
+      // Third checkpoint
+      vi.setSystemTime(startTime + 45);
+      timer.checkpoint('step3');
+
+      expect(cli.log.debug).toHaveBeenCalledTimes(3);
+      expect(cli.log.debug).toHaveBeenNthCalledWith(1, '» step1: 10ms');
+      expect(cli.log.debug).toHaveBeenNthCalledWith(2, '» step2: 15ms');
+      expect(cli.log.debug).toHaveBeenNthCalledWith(3, '» step3: 20ms');
+    });
+
+    it('should handle zero duration correctly', () => {
+      const startTime = 1000000;
+      vi.setSystemTime(startTime);
+      const timer = new Timer();
+
+      // Checkpoint immediately
+      timer.checkpoint('immediate');
+
+      expect(cli.log.debug).toHaveBeenCalledWith('» immediate: 0ms');
+    });
+
+    it('should handle custom checkpoint names', () => {
+      const startTime = 1000000;
+      vi.setSystemTime(startTime);
+      const timer = new Timer();
+
+      vi.setSystemTime(startTime + 200);
+      timer.checkpoint('Custom Checkpoint Name');
+
+      expect(cli.log.debug).toHaveBeenCalledWith(
+        '» Custom Checkpoint Name: 200ms'
+      );
+    });
+  });
+});