testland/test-isolation-patterns
Pure reference catalog of test-isolation and fixture-lifecycle patterns - the four-phase test pattern (Meszaros), fixture scope (per-test / per-describe / shared / global), the Fresh-Fixture vs Shared-Fixture trade-off (Fowler), parallel-safety patterns, and cleanup discipline (afterEach / afterAll / tagged-cleanup), plus a pattern-selection guide and a worked leaking-state diagnosis. The database-isolation strategies (transaction-rollback / database-per-worker / template-database) and network / external-service stubbing live in references/. This is the architecture-tier reference, not a file-level fixture-coupling style rule. Use when designing fixture scope and isolation strategy, auditing fixture coupling or retry/wait policy, or moving a suite to parallel execution.
88
88%
Does it follow best practices?
Impact
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Average score across 10 eval scenarios
Passed
No findings from the security scan
Evaluation results
22 of our 26 minutes of test time is the setup hook
configure() works everywhere except inside our test file
Half the suite started misbehaving after we wrapped every test in a transaction
Integration suite takes 40 minutes and still flakes
Moving the suite to parallel workers
One broken assertion reported four failures and we could not find the real one
Our test helpers create four kinds of row and we only ever delete one of them
Rate limiter tests fail depending on what ran before them
Two cart tests fail and the two that break them look harmless
We namespaced everything per worker and still fail one run in twenty
- Agent
- Claude Code
- Model
- Claude Sonnet 4.6