Writes and runs Jest unit tests for NestJS services and controllers.
npx skills add https://github.com/lucaszhh/agents --skill nestjs-unit-tester-lucaszhh
Please help me install this Agent Skill. Skill: nestjs-unit-tester Source: https://github.com/lucaszhh/agents/tree/main/skills/back/nestjs-unit-tester Command: npx skills add https://github.com/lucaszhh/agents --skill nestjs-unit-tester-lucaszhh
*.spec.ts files next to the code under test using an official template with TestingModule, jest-mock-extended typed mocks, and Arrange-Act-Assert structure. - Result pattern validation: Tests both isSuccess and isFailure paths, and verifies controllers map errors to HttpException. - Coverage enforcement: Runs focused coverage with pnpm test -- <spec> --coverage and requires a minimum of 85% on lines and branches. - Use Case: After implementing a new NestJS service, ask the agent to write its unit tests; it writes the spec directly to disk and reports only test signatures and coverage metrics in chat. ## Quick Start Write unit tests with coverage for the demand service in src/modules/demands/domain/services/demand.service.ts.High-intent search queries and answers about installing and using this skill.
Create a spec file next to the service, build an isolated TestingModule with Test.createTestingModule, and mock every constructor dependency. Structure each test with the Arrange-Act-Assert pattern and clear mocks in beforeEach with jest.clearAllMocks().
Use jest-mock-extended to create typed mocks of repository interfaces and provide them via useValue in the TestingModule. This avoids fragile plain-object mocks that break when interfaces change.
AAA stands for Arrange, Act, Assert: first configure inputs and mock responses, then execute the method under test, then verify outcomes with expect(). It keeps each test focused and readable.
Assert result.isSuccess is true and check getValue() for happy paths, and assert result.isFailure is true with getError() returning the expected error type like NotFound for failure cases. Controllers should be verified to throw HttpException on failure.
This workflow enforces a strict minimum of 85% coverage on lines and branches for the file under test. Run pnpm test with --coverage and --collectCoverageFrom targeting the source file to verify the threshold.
Skip new tests for cosmetic changes or renames that add no logic, as long as existing assertions still pass. Unit tests are also not the right tool for architecture design or fixing production bugs directly.
k3sdtwImplement end-to-end tests for NestJS services using Jest and Supertest.
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