test: add Phase 4 database integration tests (partial)

- Add comprehensive test utilities for database testing
- Implement connection management tests for in-memory and file databases
- Add transaction tests including nested transactions and savepoints
- Test database lifecycle, error handling, and performance
- Include tests for WAL mode, connection pooling, and constraints

Part of Phase 4: Integration Testing

tests/setup/msw-setup.ts

@@ -0,0 +1,171 @@
+import { setupServer } from 'msw/node';
+import { HttpResponse, http, RequestHandler } from 'msw';
+import { afterAll, afterEach, beforeAll } from 'vitest';
+
+// Import handlers from our centralized location
+import { handlers as defaultHandlers } from '../mocks/n8n-api/handlers';
+
+// Create the MSW server instance with default handlers
+export const server = setupServer(...defaultHandlers);
+
+// Enable request logging in development/debugging
+if (process.env.MSW_DEBUG === 'true' || process.env.TEST_DEBUG === 'true') {
+  server.events.on('request:start', ({ request }) => {
+    console.log('[MSW] %s %s', request.method, request.url);
+  });
+
+  server.events.on('request:match', ({ request }) => {
+    console.log('[MSW] Request matched:', request.method, request.url);
+  });
+
+  server.events.on('request:unhandled', ({ request }) => {
+    console.warn('[MSW] Unhandled request:', request.method, request.url);
+  });
+
+  server.events.on('response:mocked', ({ request, response }) => {
+    console.log('[MSW] Mocked response for %s %s: %d', 
+      request.method, 
+      request.url, 
+      response.status
+    );
+  });
+}
+
+// Start server before all tests
+beforeAll(() => {
+  server.listen({
+    onUnhandledRequest: process.env.CI === 'true' ? 'error' : 'warn',
+  });
+});
+
+// Reset handlers after each test (important for test isolation)
+afterEach(() => {
+  server.resetHandlers();
+});
+
+// Clean up after all tests
+afterAll(() => {
+  server.close();
+});
+
+/**
+ * Utility function to add temporary handlers for specific tests
+ * @param handlers Array of MSW request handlers
+ */
+export function useHandlers(...handlers: RequestHandler[]) {
+  server.use(...handlers);
+}
+
+/**
+ * Utility to wait for a specific request to be made
+ * Useful for testing async operations
+ */
+export function waitForRequest(method: string, url: string | RegExp): Promise<Request> {
+  return new Promise((resolve) => {
+    server.events.on('request:match', ({ request }) => {
+      if (request.method === method && 
+          (typeof url === 'string' ? request.url === url : url.test(request.url))) {
+        resolve(request);
+      }
+    });
+  });
+}
+
+/**
+ * Create a handler factory for common n8n API patterns
+ */
+export const n8nHandlerFactory = {
+  // Workflow endpoints
+  workflow: {
+    list: (workflows: any[] = []) => 
+      http.get('*/api/v1/workflows', () => {
+        return HttpResponse.json({ data: workflows, nextCursor: null });
+      }),
+    
+    get: (id: string, workflow: any) =>
+      http.get(`*/api/v1/workflows/${id}`, () => {
+        return HttpResponse.json({ data: workflow });
+      }),
+    
+    create: () =>
+      http.post('*/api/v1/workflows', async ({ request }) => {
+        const body = await request.json();
+        return HttpResponse.json({ 
+          data: { 
+            id: 'mock-workflow-id', 
+            ...body,
+            createdAt: new Date().toISOString(),
+            updatedAt: new Date().toISOString()
+          } 
+        });
+      }),
+    
+    update: (id: string) =>
+      http.patch(`*/api/v1/workflows/${id}`, async ({ request }) => {
+        const body = await request.json();
+        return HttpResponse.json({ 
+          data: { 
+            id, 
+            ...body,
+            updatedAt: new Date().toISOString()
+          } 
+        });
+      }),
+    
+    delete: (id: string) =>
+      http.delete(`*/api/v1/workflows/${id}`, () => {
+        return HttpResponse.json({ success: true });
+      }),
+  },
+
+  // Execution endpoints
+  execution: {
+    list: (executions: any[] = []) =>
+      http.get('*/api/v1/executions', () => {
+        return HttpResponse.json({ data: executions, nextCursor: null });
+      }),
+    
+    get: (id: string, execution: any) =>
+      http.get(`*/api/v1/executions/${id}`, () => {
+        return HttpResponse.json({ data: execution });
+      }),
+  },
+
+  // Webhook endpoints
+  webhook: {
+    trigger: (webhookUrl: string, response: any = { success: true }) =>
+      http.all(webhookUrl, () => {
+        return HttpResponse.json(response);
+      }),
+  },
+
+  // Error responses
+  error: {
+    notFound: (resource: string = 'resource') =>
+      HttpResponse.json(
+        { message: `${resource} not found`, code: 'NOT_FOUND' },
+        { status: 404 }
+      ),
+    
+    unauthorized: () =>
+      HttpResponse.json(
+        { message: 'Unauthorized', code: 'UNAUTHORIZED' },
+        { status: 401 }
+      ),
+    
+    serverError: (message: string = 'Internal server error') =>
+      HttpResponse.json(
+        { message, code: 'INTERNAL_ERROR' },
+        { status: 500 }
+      ),
+    
+    validationError: (errors: any) =>
+      HttpResponse.json(
+        { message: 'Validation failed', errors, code: 'VALIDATION_ERROR' },
+        { status: 400 }
+      ),
+  }
+};
+
+// Export for use in tests
+export { http, HttpResponse } from 'msw';