Diagnosable Tests

Bazuzi’s name for Beck’s Specific, adopted because it states the goal: when a test fails, the cause should be obvious from the failure alone. The ideal is Bazuzi’s “1 defect == 1 test failure”: a single broken behavior lights up exactly one test, and its message carries the offending input.

Eager tests (one test asserting many behaviors) and assertion roulette (which assert fired?) are the classic smells, both named by Meszaros. Diagnosability leans on readability and on order independence; a cascade of collateral failures diagnoses nothing.

Part of Test Desiderata.

Measuring: mean time from red CI to fix commit, assertion-message completeness, and mutants killed per test (a test killing many unrelated mutants is doing too much).