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Docs: a proven new test starts at tier B; tier C is for unproven tests #840

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lmoresi merged 1 commit into from
Oct 11, 2026
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Docs: a proven new test starts at tier B; tier C is for unproven tests #840

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9 changes: 5 additions & 4 deletions CLAUDE.md
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Expand Up @@ -204,10 +204,11 @@ pytest -m "level_1 and tier_a" # quick
pytest -m "tier_a or tier_b" # full validation
```

Tier A is hardened and reviewed — safe to build code around. Tier C is not mature
enough to drive coding. Every bug fix ships the regression test that would have
caught it, written first and shown to fail. Validate a new test's own correctness
before changing library code to satisfy it.
Tier A is hardened and reviewed — safe to build code around. Every bug fix ships
the regression test that would have caught it, written first and shown to fail;
such a proven test starts at tier B, so it gates. Tier C is only for a test not yet
proven, so it cannot derail the code. Validate a new test's own correctness before
changing library code to satisfy it.

Every test file must be reachable from a glob in `scripts/test.sh`;
`scripts/check_test_coverage.py` enforces it.
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8 changes: 6 additions & 2 deletions docs/developer/TESTING-RELIABILITY-SYSTEM.md
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Expand Up @@ -291,11 +291,15 @@ pytest -m "not tier_c"

### When Writing a New Test

1. **Start at Tier C**: All new tests begin as experimental
1. **A proven test starts at Tier B**: a regression test written first and shown to
fail without the fix it guards, or a test asserting a hard baseline whose own
correctness has been checked, gates from the start. Tier C is for a test that is
not yet proven, so that it cannot derail the code it was written against (the C2
population above); it is otherwise close to obsolete (Louis, 2026-10-11).
2. **Document Intent**: Clear docstring explaining what behavior is tested
3. **Use xfail Appropriately**: If testing unimplemented feature, mark with xfail
4. **Don't Break CI**: Tier C tests with xfail won't break automated testing
5. **Promote Deliberately**: Don't rush promotion - let tests prove reliability
5. **Promote Deliberately**: Tier B → A is the review step described above

### When a Test Fails

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2 changes: 1 addition & 1 deletion tests/test_0025_jit_compile_flags.py
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Expand Up @@ -14,7 +14,7 @@

import underworld3 as uw

pytestmark = [pytest.mark.level_1, pytest.mark.tier_c]
pytestmark = [pytest.mark.level_1, pytest.mark.tier_b]


def _compile_args(bundles):
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