Loop 011
The test-suite speed loop
A performance workflow for reducing test runtime under repeatable conditions without weakening coverage, assertions, isolation, or behavior.
Ready-to-use prompt
Copy the loop
Optimize the test suite to run as quickly as possible without reducing coverage or changing behavior.
Verify / stop
The suite is faster with no coverage or behavior regression.
Repeatable timing, the full passing suite, and the original coverage report prove the result.
Context and guidance When to use it, steps, safety notes, and related loops
Use this when
Use this when slow tests are delaying local feedback or continuous integration and the project has stable commands for measuring runtime and coverage.
How to run it
- Record the full-suite runtime, coverage, environment, worker settings, and repeatable timing method.
- Profile the suite to find expensive setup, redundant work, poor isolation, unnecessary integration paths, or safe parallelization opportunities.
- Make one optimization at a time, then rerun the full suite and compare timing, coverage, and behavior.
- Stop at the agreed runtime target or diminishing-returns rule with all original checks still passing.
Why it works
A fixed baseline prevents speed work from quietly trading away coverage or correctness. Profiling directs effort toward measured bottlenecks instead of speculative rewrites.
Implementation note
Define a runtime target or diminishing-returns rule before starting. Faster tests are not an improvement if they become flaky, order-dependent, or less representative.