test: cover common logging example controller

backend/src/common/examples/example.controller.spec.ts

@@ -0,0 +1,93 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import type { Request } from 'express';
+import { ExampleController } from './example.controller';
+import { LoggerService } from '../services/logger.service';
+import { RequestContextService } from '../services/request-context.service';
+
+type MockLoggerService = Pick<LoggerService, 'log' | 'error' | 'logStructured'>;
+
+type MockRequestContextService = Pick<
+  RequestContextService,
+  'getCorrelationId' | 'getRequestId' | 'getLogContext'
+>;
+
+describe('ExampleController', () => {
+  let controller: ExampleController;
+  let logger: jest.Mocked<MockLoggerService>;
+  let requestContextService: jest.Mocked<MockRequestContextService>;
+
+  beforeEach(async () => {
+    logger = {
+      log: jest.fn(),
+      error: jest.fn(),
+      logStructured: jest.fn(),
+    };
+
+    requestContextService = {
+      getCorrelationId: jest.fn().mockReturnValue('corr-123'),
+      getRequestId: jest.fn().mockReturnValue('req-456'),
+      getLogContext: jest.fn().mockReturnValue({
+        correlationId: 'corr-123',
+        requestId: 'req-456',
+        method: 'GET',
+        url: '/v1/example',
+      }),
+    };
+
+    const module: TestingModule = await Test.createTestingModule({
+      controllers: [ExampleController],
+      providers: [
+        { provide: LoggerService, useValue: logger },
+        { provide: RequestContextService, useValue: requestContextService },
+      ],
+    }).compile();
+
+    controller = module.get(ExampleController);
+  });
+
+  it('returns context identifiers and writes structured happy-path logs', () => {
+    const response = controller.getExample({} as Request);
+
+    expect(response).toEqual({
+      message: 'Example response',
+      correlationId: 'corr-123',
+      requestId: 'req-456',
+    });
+
+    expect(logger.log).toHaveBeenCalledWith(
+      'Processing example request',
+      'ExampleController',
+    );
+    const structuredLogCall = logger.logStructured.mock.calls[0];
+    expect(structuredLogCall).toBeDefined();
+    expect(structuredLogCall[0]).toBe('info');
+    expect(structuredLogCall[1]).toBe('Example request processed');
+    expect(structuredLogCall[2]).toMatchObject({ action: 'get_example' });
+    expect(
+      typeof (structuredLogCall[2] as { timestamp?: unknown }).timestamp,
+    ).toBe('string');
+    expect(structuredLogCall[3]).toBe('ExampleController');
+    expect(logger.log).toHaveBeenCalledWith(
+      'Request context: {"correlationId":"corr-123","requestId":"req-456","method":"GET","url":"/v1/example"}',
+      'ExampleController',
+    );
+    expect(requestContextService.getCorrelationId).toHaveBeenCalledTimes(1);
+    expect(requestContextService.getRequestId).toHaveBeenCalledTimes(1);
+  });
+
+  it('logs structured error details before surfacing the failure', () => {
+    expect(() => controller.getError()).toThrow('Test error');
+
+    expect(logger.error).toHaveBeenCalledWith(
+      'This is a test error',
+      '',
+      'ExampleController',
+    );
+    expect(logger.logStructured).toHaveBeenCalledWith(
+      'error',
+      'Test error occurred',
+      { error: 'Test error', details: 'This is a test error message' },
+      'ExampleController',
+    );
+  });
+});