Agent-skills-standard 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)

install

source · Clone the upstream repo

git clone https://github.com/HoangNguyen0403/agent-skills-standard

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/HoangNguyen0403/agent-skills-standard "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/nestjs/nestjs-testing" ~/.claude/skills/hoangnguyen0403-agent-skills-standard-nestjs-testing && rm -rf "$T"

manifest: skills/nestjs/nestjs-testing/SKILL.md

source content

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

Strict-TypeScript patterns (Jest matchers, mock typing, DTO verification): references/strict-typescript-testing.md