Swift Testing

Tests prove observable contracts. Coverage is supporting structural evidence, not behavioral equivalence.

Test design

Name the source test, contract, defect, risk, or incident protected by each test.
Assert values, typed errors, ordering, state transitions, side effects, bytes, cleanup, and public lifecycle behavior.
Prefer real values and controlled fakes at owned boundaries. Mock only expensive or nondeterministic collaborators.
Preserve every parameterized source case identity during migrations even when Swift groups cases in one test declaration.
For async tests, use expectations, continuations, clocks, or event-driven hooks with bounded timeouts; avoid fixed sleeps.
Reuse one conformance suite across adapters, then add adapter-native failure and lifecycle cases.
Test every claimed platform or condition in CI; conditional compilation is part of the behavioral surface.