test(07-03): add failing tests for cookie validation

- Test validate_cookie_valid - valid cookie returns user info
- Test validate_cookie_expired - expired cookie returns False
- Test validate_cookie_empty - empty cookie returns False
- Test validate_cookie_malformed - network error handling
- Test validate_cookie_other_status_code - non-200/401 handling

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/test_auth/test_cookie_validation.py

@@ -0,0 +1,133 @@
+"""Tests for Cookie validation functionality.
+
+Tests the validate_cookie method in ZhihuLogin class.
+"""
+
+from unittest.mock import MagicMock, patch, AsyncMock
+import pytest
+
+from kb_workflow.auth.zhihu_login import ZhihuLogin, CookieValidationResult
+
+
+class TestCookieValidation:
+    """Test suite for cookie validation."""
+
+    @pytest.fixture
+    def mock_browser_with_request(self):
+        """Mock browser with request API support."""
+        browser = MagicMock()
+        browser.browser = MagicMock()
+        browser.page = MagicMock()
+
+        # Create mock response
+        mock_response = MagicMock()
+        mock_response.status = 200
+        mock_response.json = AsyncMock(return_value={
+            "id": 12345678,
+            "name": "TestUser",
+            "url_token": "testuser"
+        })
+
+        # Setup page.request.get to return mock response
+        browser.page.request = MagicMock()
+        browser.page.request.get = AsyncMock(return_value=mock_response)
+
+        browser.close = MagicMock()
+        browser.start = MagicMock()
+
+        return browser, mock_response
+
+    @pytest.mark.asyncio
+    async def test_validate_cookie_valid(self, mock_browser_with_request, intermediate_path):
+        """Test 1: validate_cookie_valid - Valid cookie returns valid=True with user info."""
+        # Arrange
+        mock_browser, _ = mock_browser_with_request
+        login = ZhihuLogin(intermediate_path=intermediate_path)
+        login.browser = mock_browser
+
+        # Act
+        result = await login.validate_cookie("z_c0=valid_cookie_value")
+
+        # Assert
+        assert isinstance(result, CookieValidationResult)
+        assert result.valid is True
+        assert result.username == "TestUser"
+        assert result.user_id == "12345678"
+        assert result.reason is None
+
+    @pytest.mark.asyncio
+    async def test_validate_cookie_expired(self, mock_browser_with_request, intermediate_path):
+        """Test 2: validate_cookie_expired - Expired cookie returns valid=False."""
+        # Arrange
+        mock_browser, mock_response = mock_browser_with_request
+        mock_response.status = 401
+
+        login = ZhihuLogin(intermediate_path=intermediate_path)
+        login.browser = mock_browser
+
+        # Act
+        result = await login.validate_cookie("z_c0=expired_cookie_value")
+
+        # Assert
+        assert isinstance(result, CookieValidationResult)
+        assert result.valid is False
+        assert result.reason == "Cookie expired"
+        assert result.username is None
+        assert result.user_id is None
+
+    @pytest.mark.asyncio
+    async def test_validate_cookie_empty(self, intermediate_path):
+        """Test 3: validate_cookie_empty - Empty cookie returns valid=False."""
+        # Arrange
+        login = ZhihuLogin(intermediate_path=intermediate_path)
+        login.browser = MagicMock()
+        login.browser.page = None  # No page means no cookie loaded
+
+        # Act
+        result = await login.validate_cookie()
+
+        # Assert
+        assert isinstance(result, CookieValidationResult)
+        assert result.valid is False
+        assert "No cookie" in result.reason
+
+    @pytest.mark.asyncio
+    async def test_validate_cookie_malformed(self, intermediate_path):
+        """Test 4: validate_cookie_malformed - Malformed cookie returns valid=False."""
+        # Arrange
+        mock_browser = MagicMock()
+        mock_browser.browser = MagicMock()
+        mock_browser.page = MagicMock()
+        mock_browser.page.request = MagicMock()
+        mock_browser.page.request.get = AsyncMock(side_effect=Exception("Network error"))
+        mock_browser.close = MagicMock()
+        mock_browser.start = MagicMock()
+
+        login = ZhihuLogin(intermediate_path=intermediate_path)
+        login.browser = mock_browser
+
+        # Act
+        result = await login.validate_cookie("invalid_format_cookie")
+
+        # Assert
+        assert isinstance(result, CookieValidationResult)
+        assert result.valid is False
+        assert "Network error" in result.reason
+
+    @pytest.mark.asyncio
+    async def test_validate_cookie_other_status_code(self, mock_browser_with_request, intermediate_path):
+        """Test 5: validate_cookie with non-200/401 status code."""
+        # Arrange
+        mock_browser, mock_response = mock_browser_with_request
+        mock_response.status = 500
+
+        login = ZhihuLogin(intermediate_path=intermediate_path)
+        login.browser = mock_browser
+
+        # Act
+        result = await login.validate_cookie("z_c0=some_cookie")
+
+        # Assert
+        assert isinstance(result, CookieValidationResult)
+        assert result.valid is False
+        assert "500" in result.reason