Generate unit tests using Jest with mocking, AAA pattern (Arrange-Act-Assert), and 80%+ coverage target. Use when testing business logic, handlers, or services in isolation.
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---
name: api-test-unit
description: Generate unit tests using Jest with mocking, AAA pattern (Arrange-Act-Assert), and 80%+ coverage target. Use when testing business logic, handlers, or services in isolation.
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---
# Unit Tests
## Purpose
Generate unit tests using **Jest** with proper mocking of dependencies, AAA pattern (Arrange-Act-Assert), and descriptive test names.
## Why Jest Instead of node:test?
This repository uses **Jest** for ALL testing instead of Node.js's built-in `node:test` runner:
- **Issue**: [nestjs/nest#14130](https://github.com/nestjs/nest/issues/14130) - NestJS `@nestjs/testing` is incompatible with `node:test`
- **Impact**: `node:test` cannot properly inject `QueryBus`, `CommandBus`, or other NestJS providers
- **Solution**: Jest provides full compatibility with NestJS's testing utilities and DI system
## When to Use
- Testing business logic in isolation
- Testing command/query handlers
- Testing repository methods
- Testing service methods
- Unit testing utilities
## What It Generates
### Directory Structure
```
apps/api/src/modules/{feature}/__tests__/**/*.test.ts
```
Tests are co-located with source code but cleanly separated in `__tests__/` subdirectory.
## Patterns Enforced
### AAA Pattern
All tests follow Arrange-Act-Assert:
- **Arrange**: Set up test data and mocks
- **Act**: Execute the function under test
- **Assert**: Verify expected outcomes
### Descriptive Test Names
Test names should describe:
- What is being tested
- The expected outcome
- Edge cases covered
Example: `should create user when valid data provided`
### Mocking
- Mock external dependencies
- Mock database calls
- Mock event bus
- Verify mock calls
### Coverage Target
- 80%+ code coverage
- Test success and failure paths
- Test edge cases
## Usage Example
```bash
/skill test-unit --name=CreateUserHandler --type=command-handler --scenarios='success,duplicate-email,database-error'
```
## Related Files
- [Test Integration](../test-integration/SKILL.md) - Integration tests
- [Test E2E](../test-e2e/SKILL.md) - E2E tests
- [Feature CQRS](../../core/feature-cqrs/SKILL.md) - Handlers to test
