diff --git a/package.json b/package.json
index 8c13e80..7dc9548 100644
--- a/package.json
+++ b/package.json
@@ -13,7 +13,9 @@
     "dev": "tsx src/index.ts",
     "typecheck": "tsc --noEmit",
     "format": "prettier --write 'src/**/*.ts'",
-    "format:check": "prettier --check 'src/**/*.ts'"
+    "format:check": "prettier --check 'src/**/*.ts'",
+    "test": "vitest run",
+    "test:watch": "vitest"
   },
   "keywords": [
     "browser",
@@ -33,6 +35,7 @@
     "@types/node": "^20.10.0",
     "prettier": "^3.7.4",
     "tsx": "^4.6.0",
-    "typescript": "^5.3.0"
+    "typescript": "^5.3.0",
+    "vitest": "^4.0.16"
   }
 }
diff --git a/src/browser.test.ts b/src/browser.test.ts
new file mode 100644
index 0000000..b20ff71
--- /dev/null
+++ b/src/browser.test.ts
@@ -0,0 +1,157 @@
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import { BrowserManager } from './browser.js';
+
+describe('BrowserManager', () => {
+  let browser: BrowserManager;
+
+  beforeAll(async () => {
+    browser = new BrowserManager();
+    await browser.launch({ headless: true });
+  });
+
+  afterAll(async () => {
+    await browser.close();
+  });
+
+  describe('launch and close', () => {
+    it('should report as launched', () => {
+      expect(browser.isLaunched()).toBe(true);
+    });
+
+    it('should have a page', () => {
+      const page = browser.getPage();
+      expect(page).toBeDefined();
+    });
+  });
+
+  describe('navigation', () => {
+    it('should navigate to URL', async () => {
+      const page = browser.getPage();
+      await page.goto('https://example.com');
+      expect(page.url()).toBe('https://example.com/');
+    });
+
+    it('should get page title', async () => {
+      const page = browser.getPage();
+      const title = await page.title();
+      expect(title).toBe('Example Domain');
+    });
+  });
+
+  describe('element interaction', () => {
+    it('should find element by selector', async () => {
+      const page = browser.getPage();
+      const heading = await page.locator('h1').textContent();
+      expect(heading).toBe('Example Domain');
+    });
+
+    it('should check element visibility', async () => {
+      const page = browser.getPage();
+      const isVisible = await page.locator('h1').isVisible();
+      expect(isVisible).toBe(true);
+    });
+
+    it('should count elements', async () => {
+      const page = browser.getPage();
+      const count = await page.locator('p').count();
+      expect(count).toBeGreaterThan(0);
+    });
+  });
+
+  describe('screenshots', () => {
+    it('should take screenshot as buffer', async () => {
+      const page = browser.getPage();
+      const buffer = await page.screenshot();
+      expect(buffer).toBeInstanceOf(Buffer);
+      expect(buffer.length).toBeGreaterThan(0);
+    });
+  });
+
+  describe('evaluate', () => {
+    it('should evaluate JavaScript', async () => {
+      const page = browser.getPage();
+      const result = await page.evaluate(() => document.title);
+      expect(result).toBe('Example Domain');
+    });
+
+    it('should evaluate with arguments', async () => {
+      const page = browser.getPage();
+      const result = await page.evaluate((x: number) => x * 2, 5);
+      expect(result).toBe(10);
+    });
+  });
+
+  describe('tabs', () => {
+    it('should create new tab', async () => {
+      const result = await browser.newTab();
+      expect(result.index).toBe(1);
+      expect(result.total).toBe(2);
+    });
+
+    it('should list tabs', async () => {
+      const tabs = await browser.listTabs();
+      expect(tabs.length).toBe(2);
+    });
+
+    it('should close tab', async () => {
+      // Switch to second tab and close it
+      const page = browser.getPage();
+      const tabs = await browser.listTabs();
+      if (tabs.length > 1) {
+        const result = await browser.closeTab(1);
+        expect(result.remaining).toBe(1);
+      }
+    });
+  });
+
+  describe('context operations', () => {
+    it('should get cookies from context', async () => {
+      const page = browser.getPage();
+      const cookies = await page.context().cookies();
+      expect(Array.isArray(cookies)).toBe(true);
+    });
+
+    it('should set and get cookies', async () => {
+      const page = browser.getPage();
+      const context = page.context();
+      await context.addCookies([{ name: 'test', value: 'value', url: 'https://example.com' }]);
+      const cookies = await context.cookies();
+      const testCookie = cookies.find((c) => c.name === 'test');
+      expect(testCookie?.value).toBe('value');
+    });
+
+    it('should clear cookies', async () => {
+      const page = browser.getPage();
+      const context = page.context();
+      await context.clearCookies();
+      const cookies = await context.cookies();
+      expect(cookies.length).toBe(0);
+    });
+  });
+
+  describe('storage via evaluate', () => {
+    it('should set and get localStorage', async () => {
+      const page = browser.getPage();
+      await page.evaluate(() => localStorage.setItem('testKey', 'testValue'));
+      const value = await page.evaluate(() => localStorage.getItem('testKey'));
+      expect(value).toBe('testValue');
+    });
+
+    it('should clear localStorage', async () => {
+      const page = browser.getPage();
+      await page.evaluate(() => localStorage.clear());
+      const value = await page.evaluate(() => localStorage.getItem('testKey'));
+      expect(value).toBeNull();
+    });
+  });
+
+  describe('viewport', () => {
+    it('should set viewport', async () => {
+      await browser.setViewport(1920, 1080);
+      const page = browser.getPage();
+      const size = page.viewportSize();
+      expect(size?.width).toBe(1920);
+      expect(size?.height).toBe(1080);
+    });
+  });
+});
diff --git a/src/protocol.test.ts b/src/protocol.test.ts
new file mode 100644
index 0000000..41e223a
--- /dev/null
+++ b/src/protocol.test.ts
@@ -0,0 +1,216 @@
+import { describe, it, expect } from 'vitest';
+import { parseCommand } from './protocol.js';
+
+// Helper to create command JSON string
+const cmd = (obj: object) => JSON.stringify(obj);
+
+describe('parseCommand', () => {
+  describe('navigation', () => {
+    it('should parse navigate command', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'navigate', url: 'https://example.com' }));
+      expect(result.success).toBe(true);
+      if (result.success) {
+        expect(result.command.action).toBe('navigate');
+        expect(result.command.url).toBe('https://example.com');
+      }
+    });
+
+    it('should reject navigate without url', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'navigate' }));
+      expect(result.success).toBe(false);
+    });
+  });
+
+  describe('click', () => {
+    it('should parse click command', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'click', selector: '#btn' }));
+      expect(result.success).toBe(true);
+      if (result.success) {
+        expect(result.command.action).toBe('click');
+        expect(result.command.selector).toBe('#btn');
+      }
+    });
+
+    it('should reject click without selector', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'click' }));
+      expect(result.success).toBe(false);
+    });
+  });
+
+  describe('type', () => {
+    it('should parse type command', () => {
+      const result = parseCommand(
+        cmd({ id: '1', action: 'type', selector: '#input', text: 'hello' })
+      );
+      expect(result.success).toBe(true);
+      if (result.success) {
+        expect(result.command.action).toBe('type');
+        expect(result.command.selector).toBe('#input');
+        expect(result.command.text).toBe('hello');
+      }
+    });
+  });
+
+  describe('fill', () => {
+    it('should parse fill command', () => {
+      const result = parseCommand(
+        cmd({ id: '1', action: 'fill', selector: '#input', value: 'hello' })
+      );
+      expect(result.success).toBe(true);
+      if (result.success) {
+        expect(result.command.action).toBe('fill');
+        expect(result.command.value).toBe('hello');
+      }
+    });
+  });
+
+  describe('wait', () => {
+    it('should parse wait with selector', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'wait', selector: '#loading' }));
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse wait with timeout', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'wait', timeout: 5000 }));
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse wait with text', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'wait', text: 'Welcome' }));
+      expect(result.success).toBe(true);
+    });
+  });
+
+  describe('screenshot', () => {
+    it('should parse screenshot command', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'screenshot', path: 'test.png' }));
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse screenshot with fullPage', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'screenshot', fullPage: true }));
+      expect(result.success).toBe(true);
+    });
+  });
+
+  describe('cookies', () => {
+    it('should parse cookies_get', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'cookies_get' }));
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse cookies_set', () => {
+      const result = parseCommand(
+        cmd({
+          id: '1',
+          action: 'cookies_set',
+          cookies: [{ name: 'session', value: 'abc123' }],
+        })
+      );
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse cookies_clear', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'cookies_clear' }));
+      expect(result.success).toBe(true);
+    });
+  });
+
+  describe('storage', () => {
+    it('should parse storage_get', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'storage_get', type: 'local' }));
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse storage_set', () => {
+      const result = parseCommand(
+        cmd({
+          id: '1',
+          action: 'storage_set',
+          type: 'local',
+          key: 'test',
+          value: 'value',
+        })
+      );
+      expect(result.success).toBe(true);
+    });
+  });
+
+  describe('semantic locators', () => {
+    it('should parse getbyrole', () => {
+      const result = parseCommand(
+        cmd({
+          id: '1',
+          action: 'getbyrole',
+          role: 'button',
+          subaction: 'click',
+        })
+      );
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse getbytext', () => {
+      const result = parseCommand(
+        cmd({
+          id: '1',
+          action: 'getbytext',
+          text: 'Submit',
+          subaction: 'click',
+        })
+      );
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse getbylabel', () => {
+      const result = parseCommand(
+        cmd({
+          id: '1',
+          action: 'getbylabel',
+          label: 'Email',
+          subaction: 'fill',
+          value: 'test@test.com',
+        })
+      );
+      expect(result.success).toBe(true);
+    });
+  });
+
+  describe('tabs', () => {
+    it('should parse tab_new', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'tab_new' }));
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse tab_list', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'tab_list' }));
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse tab_switch', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'tab_switch', index: 0 }));
+      expect(result.success).toBe(true);
+    });
+
+    it('should parse tab_close', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'tab_close' }));
+      expect(result.success).toBe(true);
+    });
+  });
+
+  describe('invalid commands', () => {
+    it('should reject unknown action', () => {
+      const result = parseCommand(cmd({ id: '1', action: 'unknown' }));
+      expect(result.success).toBe(false);
+    });
+
+    it('should reject missing id', () => {
+      const result = parseCommand(cmd({ action: 'click', selector: '#btn' }));
+      expect(result.success).toBe(false);
+    });
+
+    it('should reject invalid JSON', () => {
+      const result = parseCommand('not json');
+      expect(result.success).toBe(false);
+    });
+  });
+});
diff --git a/vitest.config.ts b/vitest.config.ts
new file mode 100644
index 0000000..46ef8ae
--- /dev/null
+++ b/vitest.config.ts
@@ -0,0 +1,9 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    include: ['src/**/*.test.ts'],
+    testTimeout: 30000,
+  },
+});