Testing Strategy

Testing Strategy

Critical rules

• Pyramid: many fast unit tests → fewer integration → thin load/chaos top.
• Unit tests mock deps with mock<DepsType>() / mockDeep — never vi.mock for app modules.
• Integration tests use real localhost DB only; guardrails must throw on non-localhost URLs.
• Name by type: *.test.ts (unit), *.test.int.ts (integration), load/*.js, chaos/*.
• Hard to test = design smell (fn-args-deps mocks only what the function uses).
• Faker for realistic unique fixtures so tests parallelize without cleanup.
• Before long setup/Prisma/Faker examples, read the matching resource below.

Workflow

1. Pick the layer by the question:
   • Logic / injectable deps? → Unit (mock deps, ms)
   • Crosses real boundary (DB, FS)? → Integration (.test.int.ts, localhost)
   • Concurrent traffic / SLOs? → Load (performance-testing)
   • Survive dependency failure? → Chaos (performance-testing)
2. Unit: typed mocks from the deps interface; assert Results and values (writing-tests).
3. Integration: real DB, seed unique Faker data, query only that data.
4. Ensure vitest.setup.ts enforces localhost DB + vi.clearAllMocks() between tests.
5. Prisma fluent API: mockDeep<PrismaClient>() (+ $transaction callback helper).
6. Load/chaos: critical paths only — see performance-testing.

Resources

• references/examples.md — unit/integration/Prisma/Faker patterns. Read when implementing a layer.
• references/setup.md — file naming, guardrails, vitest config, load smoke sketch. Read when scaffolding the suite.
• references/rationalizations.md — excuse→reality and red flags. Read when tempted to skip the pyramid.

Validation

• Each test at the right pyramid layer
• Unit: mock<DepsType>(), no app-module vi.mock
• Integration: .test.int.ts + localhost-only guardrail
• Prisma via mockDeep; Faker unique IDs/emails for parallel runs
• Setup clears mocks between tests

Constraints

• Not the red-green-refactor loop (tdd-workflow) or assertion craft (writing-tests).
• Deep k6 profiles and Toxiproxy live in performance-testing.
• Adjacent: fn-args-deps, result-types.