Testing Guidelines

Principles

• Test cases are independent — no shared mutable state between tests.
• Test public interfaces, not internal implementation.
• Unit-test the happy path and all boundary cases.
• Tests are deterministic — no sleep, no wall-clock time, no unfixed random seeds.
• Inject clocks, UUID generators etc. that are controllable by the test driver
• No network or file-system access in unit tests.

Test Pyramid (Martin Fowler)

• Unit tests — fast, isolated, the majority. Mock only at architectural boundaries.
• Integration tests — test component interactions at boundaries; always use BDD; may be written in a different language (e.g., Python/Behave).
• End-to-end tests — minimal; critical user journeys only.

BDD

• Use cases are covered by BDD integration tests.
• Structure: Given / When / Then.
• Preferred frameworks: Godog (Go), Behave (Python), Catch2 (C++), Cucumber + JUnit 5 (Java).

Mocking

• Mock only at layer boundaries (e.g., infra interfaces defined in usecase).
• Never mock domain or use-case logic — test it directly.

Test Data

• Use builders or factories; avoid large inline literals.
• Never depend on test execution order.