nestjs-testing
Write Unit and E2E tests with Jest, mocking strategies, and database isolation in NestJS. Use when writing NestJS unit tests, E2E tests with supertest, or mock providers. (triggers: **/*.spec.ts, test/**/*.e2e-spec.ts, Test.createTestingModule, supertest, jest, beforeEach)
Best use case
nestjs-testing is best used when you need a repeatable AI agent workflow instead of a one-off prompt.
Write Unit and E2E tests with Jest, mocking strategies, and database isolation in NestJS. Use when writing NestJS unit tests, E2E tests with supertest, or mock providers. (triggers: **/*.spec.ts, test/**/*.e2e-spec.ts, Test.createTestingModule, supertest, jest, beforeEach)
Teams using nestjs-testing should expect a more consistent output, faster repeated execution, less prompt rewriting.
When to use this skill
- You want a reusable workflow that can be run more than once with consistent structure.
When not to use this skill
- You only need a quick one-off answer and do not need a reusable workflow.
- You cannot install or maintain the underlying files, dependencies, or repository context.
Installation
Claude Code / Cursor / Codex
Manual Installation
- Download SKILL.md from GitHub
- Place it in
.claude/skills/nestjs-testing/SKILL.mdinside your project - Restart your AI agent — it will auto-discover the skill
How nestjs-testing Compares
| Feature / Agent | nestjs-testing | Standard Approach |
|---|---|---|
| Platform Support | Not specified | Limited / Varies |
| Context Awareness | High | Baseline |
| Installation Complexity | Unknown | N/A |
Frequently Asked Questions
What does this skill do?
Write Unit and E2E tests with Jest, mocking strategies, and database isolation in NestJS. Use when writing NestJS unit tests, E2E tests with supertest, or mock providers. (triggers: **/*.spec.ts, test/**/*.e2e-spec.ts, Test.createTestingModule, supertest, jest, beforeEach)
Where can I find the source code?
You can find the source code on GitHub using the link provided at the top of the page.
SKILL.md Source
# NestJS Testing
## **Priority: P2 (MAINTENANCE)**
## Structure
```
src/**/*.spec.ts # Unit tests (isolated logic)
test/**/*.e2e-spec.ts # E2E tests (full app flows)
```
## Unit Testing
- **Setup**: Use `Test.createTestingModule()` with mocked providers
- **Mocks**: Mock all dependencies via `{ provide: X, useValue: mockX }`
- **Pattern**: AAA (Arrange-Act-Assert)
- **Cleanup**: Call `jest.clearAllMocks()` in `afterEach`
## E2E Testing
- **Database**: Use real test DB (Docker). Never mock DB in E2E.
- **Cleanup**: Mandatory. Use transaction rollback or `TRUNCATE` in `afterEach`.
- **App Init**: Create app in `beforeAll`, close in `afterAll`
- **Guards**: Override via `.overrideGuard(X).useValue({ canActivate: () => true })`
## Strict TypeScript (MANDATORY)
- **No `any`**: Use typed objects, `jest.Mocked<T>`, or `as unknown as T`. Never `as any`.
- **No `eslint-disable`**: Fix underlying type issue. No exceptions.
- **Verify DTO shapes**: Read actual DTO class before writing mock data.
- **Cast Jest matchers**: Nested `expect.anything()` → `expect.anything() as unknown`.
- **No unused vars**: Only declare variables if referenced in assertions or setup.
## Anti-Patterns
- **No Private Tests**: Test via public methods, not `service['privateMethod']`.
When coverage requires it, use typed helper (see strict-typescript reference).
- **No DB Mocks in E2E**: Use real DB with cleanup. Mocks defeat E2E purpose.
- **No Shared State**: Call `jest.clearAllMocks()` in `afterEach`. Random failures otherwise.
- **No Resource Leaks**: Always close app and DB in `afterAll`.
## References
Setup examples, mocking patterns, E2E flows, test builders, coverage config:
[references/patterns.md](references/patterns.md)
Strict-TypeScript patterns (Jest matchers, mock typing, DTO verification):
[references/strict-typescript-testing.md](references/strict-typescript-testing.md)Related Skills
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