Testing Shared (all languages) active any

Tests isolate mutable state and clean up created resources

test-003

Intent

Tests should not pass or fail based on leftover mutable state, fixed resource names, or artifacts left behind by earlier cases.

Applicability

Applies when changed tests create files, directories, database rows, object-store objects, environment variables, accounts, caches, or other mutable shared resources. Return unknown when the relevant fixture lifecycle is outside visible scope.

What to inspect

Check fixture scopes, temp paths, shared identifiers, teardown logic, singleton resets, and whether the changed tests allocate unique resources per test or per run.

Pass criteria

Each test gets fresh mutable state or uses explicit reset and cleanup. Persistent artifacts, accounts, and paths are unique per test or run, and the teardown is visible or framework-managed.

Fail criteria

Tests mutate shared state without resetting it, reuse fixed mutable resources across runs, or leak created artifacts into later tests.

Do not flag

Immutable shared fixtures, read-only reference data, or framework-managed temp resources and rollback mechanisms that are clearly active.

Confidence guidance

HIGH when the diff mutates shared state or fixed persistent resources without cleanup. MEDIUM when cleanup may happen through unseen hooks. LOW when the fixture lifetime is unclear.

Remediation

Use per-test mutable state, unique resource names, and explicit cleanup or reset between tests.

Pass example

def test_exports_report(tmp_path):
    out = tmp_path / 'report.json'
    export_report(out)
    assert out.exists()

Fail example

SHARED_PATH = '/tmp/report.json'

def test_exports_report():
    export_report(SHARED_PATH)
    assert os.path.exists(SHARED_PATH)