Generate NestJS Unit Tests

Create comprehensive unit tests for NestJS services and controllers using Jest.

Important: Follow the Learning Mode guidelines in _templates/learning-mode.md

Arguments

• •$ARGUMENTS - File path to service/controller (e.g., "users.service.ts")

Instructions

When the user runs /nest-test <file>:

Step 1: Analyze the file

Read the target file and identify:

• •Class name and type (Service/Controller)
• •Dependencies (injected services)
• •Methods to test
• •External calls (Prisma, other services)

Step 2: Show test plan

📋 Test Plan for: UsersService

Methods to test:
1. findAll() - List users
2. findOne(id) - Get single user
3. create(dto) - Create user
4. update(id, dto) - Update user
5. remove(id) - Delete user

Mocks needed:
- PrismaService
- EmailService (if used)

Test file: users.service.spec.ts

Ask: "Bạn có muốn thêm/bớt test cases nào không?"

Step 3: Create test file

Location: Same folder as source file Naming: <filename>.spec.ts

Step 4: Write tests step by step

For EACH method, write:

1. •Happy path - Normal successful case
2. •Edge cases - Empty data, null values
3. •Error cases - Not found, validation errors

Test structure:

describe('UsersService', () => {
  let service: UsersService;
  let prisma: PrismaService;

  beforeEach(async () => {
    // Setup TestingModule with mocks
  });

  describe('findOne', () => {
    it('should return a user when found', async () => {
      // Arrange
      // Act
      // Assert
    });

    it('should throw NotFoundException when user not found', async () => {
      // Test error case
    });
  });
});

Step 5: Explain after each test

1. •Explain the AAA pattern (Arrange-Act-Assert)
2. •Explain WHY we mock dependencies
3. •Explain the assertion used
4. •Ask: "Bạn hiểu test này chưa?"

Testing Best Practices

1. •

   AAA Pattern:

   typescript

   // Arrange - Setup data and mocks
   const mockUser = { id: '1', email: 'test@test.com' };
   prisma.user.findUnique.mockResolvedValue(mockUser);
   
   // Act - Call the method
   const result = await service.findOne('1');
   
   // Assert - Check results
   expect(result).toEqual(mockUser);
   

2. •

   Mocking Prisma:

   typescript

   const mockPrisma = {
     user: {
       findUnique: jest.fn(),
       findMany: jest.fn(),
       create: jest.fn(),
       update: jest.fn(),
       delete: jest.fn(),
     },
   };
   

3. •

   Testing exceptions:

   typescript

   it('should throw NotFoundException', async () => {
     prisma.user.findUnique.mockResolvedValue(null);
   
     await expect(service.findOne('999'))
       .rejects.toThrow(NotFoundException);
   });
   

4. •

   Test isolation:

   • •Each test should be independent
   • •Use beforeEach to reset mocks
   • •Don't share state between tests

Example Usage

/nest-test backend/src/modules/users/users.service.ts
/nest-test backend/src/modules/auth/auth.controller.ts

Run Tests

After creating tests:

# Run specific test file
pnpm run test users.service.spec.ts

# Run with coverage
pnpm run test:cov

After Completion

Remind user:

• •"Nhớ update TRACKPAD.md với testing patterns học được!"
• •Suggest: "Chạy pnpm run test để verify tests pass"
• •Link to Jest docs if needed