Unittestable

Unittestable describes software components or code that are designed to be reliably tested through unit tests. It emphasizes isolation, determinism, and controllable dependencies to enable repeatable execution in automated test suites.

Characteristics: small, pure or deterministic functions; explicit dependencies; minimal side effects; avoidance of global state; well-defined interfaces; ability to substitute collaborators with mocks, stubs, or fakes; test-friendly error handling and boundary conditions; deterministic environment.

Techniques: dependency injection (injecting dependencies rather than creating internally); programming to interfaces; decomposition into testable units; use of test doubles; separating business logic from I/O; wrapping or abstracting external resources; use of pure functions; enabling asynchronous code with await/async maybe; small, single-responsibility components.

Benefits and challenges: improved reliability, easier maintenance, safer refactoring; but can involve upfront design cost; over-abstracting; tests may become coupled to mocks leading to brittleness; not all code is easily unit-testable; some interactions require integration tests.

Relationship: Unittestable is a practical quality that overlaps with testability; 'testable' or 'unittestable' may be used interchangeably in some contexts; it's often achieved via design principles like SOLID, clean architecture.

See also: testability, unit testing, dependency injection.