feat: implement Phase 8 integration tests for system tools

Implement comprehensive integration tests for 3 system tool handlers:
- handleHealthCheck (3 tests): API connectivity, version checking, feature availability
- handleListAvailableTools (7 tests): Tool discovery by category, configuration status, API limitations
- handleDiagnostic (9 tests): Environment checks, API status, tools availability, verbose mode

All 19 tests passing against real n8n instance.

Coverage:
- Health check: API availability verification, version information, feature discovery
- Tool listing: All categories (Workflow Management, Execution Management, System), configuration details
- Diagnostics: Environment variables, API connectivity, tool availability, troubleshooting steps, verbose debug mode

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/integration/n8n-api/system/diagnostic.test.ts

@@ -0,0 +1,268 @@
+/**
+ * Integration Tests: handleDiagnostic
+ *
+ * Tests system diagnostic functionality.
+ * Covers environment checks, API status, and verbose mode.
+ */
+
+import { describe, it, expect, beforeEach } from 'vitest';
+import { createMcpContext } from '../utils/mcp-context';
+import { InstanceContext } from '../../../../src/types/instance-context';
+import { handleDiagnostic } from '../../../../src/mcp/handlers-n8n-manager';
+
+describe('Integration: handleDiagnostic', () => {
+  let mcpContext: InstanceContext;
+
+  beforeEach(() => {
+    mcpContext = createMcpContext();
+  });
+
+  // ======================================================================
+  // Basic Diagnostic
+  // ======================================================================
+
+  describe('Basic Diagnostic', () => {
+    it('should run basic diagnostic check', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: {} } },
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      expect(response.data).toBeDefined();
+
+      const data = response.data as any;
+
+      // Verify core diagnostic fields
+      expect(data).toHaveProperty('timestamp');
+      expect(data).toHaveProperty('environment');
+      expect(data).toHaveProperty('apiConfiguration');
+      expect(data).toHaveProperty('toolsAvailability');
+      expect(data).toHaveProperty('troubleshooting');
+
+      // Verify timestamp format
+      expect(typeof data.timestamp).toBe('string');
+      const timestamp = new Date(data.timestamp);
+      expect(timestamp.toString()).not.toBe('Invalid Date');
+    });
+
+    it('should include environment variables', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: {} } },
+        mcpContext
+      );
+
+      const data = response.data as any;
+
+      expect(data.environment).toBeDefined();
+      expect(data.environment).toHaveProperty('N8N_API_URL');
+      expect(data.environment).toHaveProperty('N8N_API_KEY');
+      expect(data.environment).toHaveProperty('NODE_ENV');
+      expect(data.environment).toHaveProperty('MCP_MODE');
+
+      // API key should be masked
+      if (data.environment.N8N_API_KEY) {
+        expect(data.environment.N8N_API_KEY).toBe('***configured***');
+      }
+    });
+
+    it('should check API configuration and connectivity', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: {} } },
+        mcpContext
+      );
+
+      const data = response.data as any;
+
+      expect(data.apiConfiguration).toBeDefined();
+      expect(data.apiConfiguration).toHaveProperty('configured');
+      expect(data.apiConfiguration).toHaveProperty('status');
+
+      // In test environment, API should be configured
+      expect(data.apiConfiguration.configured).toBe(true);
+
+      // Verify API status
+      const status = data.apiConfiguration.status;
+      expect(status).toHaveProperty('configured');
+      expect(status).toHaveProperty('connected');
+
+      // Should successfully connect to n8n API
+      expect(status.connected).toBe(true);
+
+      // If connected, should have version info
+      if (status.connected) {
+        expect(status).toHaveProperty('version');
+      }
+
+      // Config details should be present when configured
+      if (data.apiConfiguration.configured) {
+        expect(data.apiConfiguration).toHaveProperty('config');
+        expect(data.apiConfiguration.config).toHaveProperty('baseUrl');
+        expect(data.apiConfiguration.config).toHaveProperty('timeout');
+        expect(data.apiConfiguration.config).toHaveProperty('maxRetries');
+      }
+    });
+
+    it('should report tools availability', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: {} } },
+        mcpContext
+      );
+
+      const data = response.data as any;
+
+      expect(data.toolsAvailability).toBeDefined();
+      expect(data.toolsAvailability).toHaveProperty('documentationTools');
+      expect(data.toolsAvailability).toHaveProperty('managementTools');
+      expect(data.toolsAvailability).toHaveProperty('totalAvailable');
+
+      // Documentation tools should always be available
+      const docTools = data.toolsAvailability.documentationTools;
+      expect(docTools.count).toBeGreaterThan(0);
+      expect(docTools.enabled).toBe(true);
+      expect(docTools.description).toBeDefined();
+
+      // Management tools should be available when API configured
+      const mgmtTools = data.toolsAvailability.managementTools;
+      expect(mgmtTools).toHaveProperty('count');
+      expect(mgmtTools).toHaveProperty('enabled');
+      expect(mgmtTools).toHaveProperty('description');
+
+      // In test environment, management tools should be enabled
+      expect(mgmtTools.enabled).toBe(true);
+      expect(mgmtTools.count).toBeGreaterThan(0);
+
+      // Total should be sum of both
+      expect(data.toolsAvailability.totalAvailable).toBe(
+        docTools.count + mgmtTools.count
+      );
+    });
+
+    it('should include troubleshooting information', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: {} } },
+        mcpContext
+      );
+
+      const data = response.data as any;
+
+      expect(data.troubleshooting).toBeDefined();
+      expect(data.troubleshooting).toHaveProperty('steps');
+      expect(data.troubleshooting).toHaveProperty('documentation');
+
+      // Troubleshooting steps should be an array
+      expect(Array.isArray(data.troubleshooting.steps)).toBe(true);
+      expect(data.troubleshooting.steps.length).toBeGreaterThan(0);
+
+      // Documentation link should be present
+      expect(typeof data.troubleshooting.documentation).toBe('string');
+      expect(data.troubleshooting.documentation).toContain('https://');
+    });
+  });
+
+  // ======================================================================
+  // Verbose Mode
+  // ======================================================================
+
+  describe('Verbose Mode', () => {
+    it('should include additional debug info in verbose mode', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: { verbose: true } } },
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+
+      // Verbose mode should add debug section
+      expect(data).toHaveProperty('debug');
+      expect(data.debug).toBeDefined();
+
+      // Verify debug information
+      expect(data.debug).toHaveProperty('processEnv');
+      expect(data.debug).toHaveProperty('nodeVersion');
+      expect(data.debug).toHaveProperty('platform');
+      expect(data.debug).toHaveProperty('workingDirectory');
+
+      // Process env should list relevant environment variables
+      expect(Array.isArray(data.debug.processEnv)).toBe(true);
+
+      // Node version should be a string
+      expect(typeof data.debug.nodeVersion).toBe('string');
+      expect(data.debug.nodeVersion).toMatch(/^v\d+\.\d+\.\d+/);
+
+      // Platform should be a string (linux, darwin, win32, etc.)
+      expect(typeof data.debug.platform).toBe('string');
+      expect(data.debug.platform.length).toBeGreaterThan(0);
+
+      // Working directory should be a path
+      expect(typeof data.debug.workingDirectory).toBe('string');
+      expect(data.debug.workingDirectory.length).toBeGreaterThan(0);
+    });
+
+    it('should not include debug info when verbose is false', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: { verbose: false } } },
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+
+      // Debug section should not be present
+      expect(data.debug).toBeUndefined();
+    });
+
+    it('should not include debug info by default', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: {} } },
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      const data = response.data as any;
+
+      // Debug section should not be present when verbose not specified
+      expect(data.debug).toBeUndefined();
+    });
+  });
+
+  // ======================================================================
+  // Response Format Verification
+  // ======================================================================
+
+  describe('Response Format', () => {
+    it('should return complete diagnostic response structure', async () => {
+      const response = await handleDiagnostic(
+        { params: { arguments: {} } },
+        mcpContext
+      );
+
+      expect(response.success).toBe(true);
+      expect(response.data).toBeDefined();
+
+      const data = response.data as any;
+
+      // Verify all required fields
+      const requiredFields = [
+        'timestamp',
+        'environment',
+        'apiConfiguration',
+        'toolsAvailability',
+        'troubleshooting'
+      ];
+
+      requiredFields.forEach(field => {
+        expect(data).toHaveProperty(field);
+        expect(data[field]).toBeDefined();
+      });
+
+      // Verify data types
+      expect(typeof data.timestamp).toBe('string');
+      expect(typeof data.environment).toBe('object');
+      expect(typeof data.apiConfiguration).toBe('object');
+      expect(typeof data.toolsAvailability).toBe('object');
+      expect(typeof data.troubleshooting).toBe('object');
+    });
+  });
+});