feat: implement integration testing foundation (Phase 1)

Complete implementation of Phase 1 foundation for n8n API integration tests.
Establishes core utilities, fixtures, and infrastructure for testing all 17 n8n API handlers against real n8n instance.

Changes:
- Add integration test environment configuration to .env.example
- Create comprehensive test utilities infrastructure:
  * credentials.ts: Environment-aware credential management (local .env vs CI secrets)
  * n8n-client.ts: Singleton API client wrapper with health checks
  * test-context.ts: Resource tracking and automatic cleanup
  * cleanup-helpers.ts: Multi-level cleanup strategies (orphaned, age-based, tag-based)
  * fixtures.ts: 6 pre-built workflow templates (webhook, HTTP, multi-node, error handling, AI, expressions)
  * factories.ts: Dynamic node/workflow builders with 15+ factory functions
  * webhook-workflows.ts: Webhook workflow configs and setup instructions

- Add npm scripts:
  * test:integration:n8n: Run n8n API integration tests
  * test:cleanup:orphans: Clean up orphaned test resources

- Create cleanup script for CI/manual use

Documentation:
- Add comprehensive integration testing plan (550 lines)
- Add Phase 1 completion summary with lessons learned

Key Features:
- Automatic credential detection (CI vs local)
- Multi-level cleanup (test, suite, CI, orphan)
- 6 workflow fixtures covering common scenarios
- 15+ factory functions for dynamic test data
- Support for 4 HTTP methods (GET, POST, PUT, DELETE) via pre-activated webhook workflows
- TypeScript-first with full type safety
- Comprehensive error handling with helpful messages

Total: ~1,520 lines of production-ready code + 650 lines of documentation

Ready for Phase 2: Workflow creation tests

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

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

tests/integration/n8n-api/utils/credentials.ts

@@ -0,0 +1,169 @@
+/**
+ * Integration Test Credentials Management
+ *
+ * Provides environment-aware credential loading for integration tests.
+ * - Local development: Reads from .env file
+ * - CI/GitHub Actions: Uses GitHub secrets from process.env
+ */
+
+import dotenv from 'dotenv';
+import path from 'path';
+
+// Load .env file for local development
+dotenv.config({ path: path.resolve(process.cwd(), '.env') });
+
+export interface N8nTestCredentials {
+  url: string;
+  apiKey: string;
+  webhookWorkflows: {
+    get: string;
+    post: string;
+    put: string;
+    delete: string;
+  };
+  cleanup: {
+    enabled: boolean;
+    tag: string;
+    namePrefix: string;
+  };
+}
+
+/**
+ * Get n8n credentials for integration tests
+ *
+ * Automatically detects environment (local vs CI) and loads
+ * credentials from the appropriate source.
+ *
+ * @returns N8nTestCredentials
+ * @throws Error if required credentials are missing
+ */
+export function getN8nCredentials(): N8nTestCredentials {
+  if (process.env.CI) {
+    // CI: Use GitHub secrets
+    return {
+      url: process.env.N8N_URL!,
+      apiKey: process.env.N8N_API_KEY!,
+      webhookWorkflows: {
+        get: process.env.N8N_TEST_WEBHOOK_GET_ID!,
+        post: process.env.N8N_TEST_WEBHOOK_POST_ID!,
+        put: process.env.N8N_TEST_WEBHOOK_PUT_ID!,
+        delete: process.env.N8N_TEST_WEBHOOK_DELETE_ID!
+      },
+      cleanup: {
+        enabled: true,
+        tag: 'mcp-integration-test',
+        namePrefix: '[MCP-TEST]'
+      }
+    };
+  } else {
+    // Local: Use .env file
+    return {
+      url: process.env.N8N_API_URL!,
+      apiKey: process.env.N8N_API_KEY!,
+      webhookWorkflows: {
+        get: process.env.N8N_TEST_WEBHOOK_GET_ID || '',
+        post: process.env.N8N_TEST_WEBHOOK_POST_ID || '',
+        put: process.env.N8N_TEST_WEBHOOK_PUT_ID || '',
+        delete: process.env.N8N_TEST_WEBHOOK_DELETE_ID || ''
+      },
+      cleanup: {
+        enabled: process.env.N8N_TEST_CLEANUP_ENABLED !== 'false',
+        tag: process.env.N8N_TEST_TAG || 'mcp-integration-test',
+        namePrefix: process.env.N8N_TEST_NAME_PREFIX || '[MCP-TEST]'
+      }
+    };
+  }
+}
+
+/**
+ * Validate that required credentials are present
+ *
+ * @param creds - Credentials to validate
+ * @throws Error if required credentials are missing
+ */
+export function validateCredentials(creds: N8nTestCredentials): void {
+  const missing: string[] = [];
+
+  if (!creds.url) {
+    missing.push(process.env.CI ? 'N8N_URL' : 'N8N_API_URL');
+  }
+  if (!creds.apiKey) {
+    missing.push('N8N_API_KEY');
+  }
+
+  if (missing.length > 0) {
+    throw new Error(
+      `Missing required n8n credentials: ${missing.join(', ')}\n\n` +
+      `Please set the following environment variables:\n` +
+      missing.map(v => `  ${v}`).join('\n') + '\n\n' +
+      `See .env.example for configuration details.`
+    );
+  }
+}
+
+/**
+ * Validate that webhook workflow IDs are configured
+ *
+ * @param creds - Credentials to validate
+ * @throws Error with setup instructions if webhook workflows are missing
+ */
+export function validateWebhookWorkflows(creds: N8nTestCredentials): void {
+  const missing: string[] = [];
+
+  if (!creds.webhookWorkflows.get) missing.push('GET');
+  if (!creds.webhookWorkflows.post) missing.push('POST');
+  if (!creds.webhookWorkflows.put) missing.push('PUT');
+  if (!creds.webhookWorkflows.delete) missing.push('DELETE');
+
+  if (missing.length > 0) {
+    const envVars = missing.map(m => `N8N_TEST_WEBHOOK_${m}_ID`);
+
+    throw new Error(
+      `Missing webhook workflow IDs for HTTP methods: ${missing.join(', ')}\n\n` +
+      `Webhook testing requires pre-activated workflows in n8n.\n` +
+      `n8n API doesn't support workflow activation, so these must be created manually.\n\n` +
+      `Setup Instructions:\n` +
+      `1. Create ${missing.length} workflow(s) in your n8n instance\n` +
+      `2. Each workflow should have a single Webhook node\n` +
+      `3. Configure webhook paths:\n` +
+      missing.map(m => `   - ${m}: mcp-test-${m.toLowerCase()}`).join('\n') + '\n' +
+      `4. ACTIVATE each workflow in n8n UI\n` +
+      `5. Set the following environment variables with workflow IDs:\n` +
+      envVars.map(v => `   ${v}=<workflow-id>`).join('\n') + '\n\n' +
+      `See docs/local/integration-testing-plan.md for detailed instructions.`
+    );
+  }
+}
+
+/**
+ * Check if credentials are configured (non-throwing version)
+ *
+ * @returns true if basic credentials are available
+ */
+export function hasCredentials(): boolean {
+  try {
+    const creds = getN8nCredentials();
+    return !!(creds.url && creds.apiKey);
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Check if webhook workflows are configured (non-throwing version)
+ *
+ * @returns true if all webhook workflow IDs are available
+ */
+export function hasWebhookWorkflows(): boolean {
+  try {
+    const creds = getN8nCredentials();
+    return !!(
+      creds.webhookWorkflows.get &&
+      creds.webhookWorkflows.post &&
+      creds.webhookWorkflows.put &&
+      creds.webhookWorkflows.delete
+    );
+  } catch {
+    return false;
+  }
+}