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Write Jest unit tests for API services following this repo's mock/factory/AppError conventions. Use when adding or extending tests in packages/api/src/tests.
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| name | write-service-test |
| description | Write Jest unit tests for API services following this repo's mock/factory/AppError conventions. Use when adding or extending tests in packages/api/src/tests. |
Jest only scans packages/api/src/tests/ (jest.config.js). Only services are unit-tested — repositories are mocked, routes/schedulers are not directly tested. Canonical example: tests/tags.service.test.ts.
Every suite follows the same five-part shape:
jest.mock('../services', () => ({
logger: { info: jest.fn(), warn: jest.fn(), error: jest.fn() },
}));
Required because services import logger from the barrel; without it the real barrel instantiates every service.
jest.Mocked<Pick<...>>type TagsRepositoryMock = jest.Mocked<Pick<TagsRepository, 'findManyForUser' | 'findOneForUser' | 'createEntity' | 'save' | 'remove'>>;
Pick only the methods the service under test calls. Import the repository/entity types with import type.
const buildTag = (overrides: Partial<Tag> = {}): Tag => ({ id: 'tag-1', userId: 'user-1', name: 'Food', ...overrides }) as Tag;
beforeEachbeforeEach(() => {
tags = { findManyForUser: jest.fn() /* ... */ } as unknown as TagsRepositoryMock;
service = new TagsService(tags as unknown as TagsRepository);
});
afterEach(() => {
jest.restoreAllMocks();
});
Constructor injection is the whole point of the repo's service design — never jest.mock the repository module.
AppError shape:await expect(service.update('user-1', 'missing', input)).rejects.toMatchObject({
message: 'Tag not found',
statusCode: 404,
});
jest.spyOn(Date, 'now').mockImplementation(() => now) and advance now manually — never real timers.For each public service method: one happy path, one per AppError branch, and edge cases (empty list, ownership miss — findOneForUser returning null). New service behaviour must land with matching tests (.agents/rules/testing.md).
npm run test:api -- <feature>.service # single suite, from root
npm run test:api -- --runInBand # full run as CI does