Establishing unit tests using vitest.

package.json

@@ -13,7 +13,7 @@
     "main.d.ts"
   ],
   "scripts": {
-    "test": "echo \"Error: no test specified\" && exit 1",
+    "test": "vitest",
     "typecheck": "tsc --noEmit",
     "build": "node esbuild.config.js",
     "play": "node play.ts",
@@ -47,7 +47,8 @@
     "arg": "^5.0.2",
     "esbuild": "^0.25.9",
     "husky": "^9.0.0",
-    "typescript": "^5.9.3"
+    "typescript": "^5.9.3",
+    "vitest": "^4.0.17"
   },
   "repository": {
     "type": "git",

tsconfig.json

@@ -5,6 +5,7 @@
     "target": "ESNext",
     "moduleResolution": "NodeNext",
     "lib": ["ESNext"],
+    "types": ["vitest/globals"],
     "allowImportingTsExtensions": true,
     "rewriteRelativeImportExtensions": true,
     "skipLibCheck": true,

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'
+      );
+    });
+  });
+});

vitest.config.ts

@@ -0,0 +1,9 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'node',
+    exclude: ['node_modules', '.temp'],
+  },
+});