Refuse done when tests/ holds no test that unittest would run (#173)

[the-ashish2005]

Defect

py-harness run "write tests for apply_discount" finished with Action: done and a success summary after writing test files that python -m unittest discover collects nothing from. Reproduced with the exact artifact from the report: discovery exits 0 with Ran 0 tests, while the harness's finish gate returned no refusal at all.

tests/test_module.py held a test method with no class around it:

def test_apply_discount(self) -> None:
        from pricing import apply_discount
        got = apply_discount(100.0, 25.0)
        self.assertEqual(got, 75.0)

It compiles, so nothing errors. Discovery imports the file, finds no TestCase subclass, collects nothing and exits 0, and the run reported success.

Root cause

_a_test_uses in src/harness/skillkit/refuse_finish.py accepted any def test_... at any scope. The orphan method names apply_discount, so the no test calls apply_discount refusal never fired and done was reachable.

The run-path half of #173 (_suite_passed, NO_TESTS_RAN) already sends the model back when a suite it ran collected nothing; what was missing is that a model answering done anyway still had to get past this oracle, and the oracle counted a method no runner calls.

Change

• tests_call/_a_test_uses now count a test only when it is a method of a class unittest discover would collect: a TestCase subclass, directly or through another class declared in the same file. Module-level def test_... functions, imports and classes with no TestCase base are no longer coverage.
• Test files are judged one at a time instead of concatenated, so one bad file cannot decide the verdict for the rest, and a file that cannot be parsed is not coverage (discovery cannot import it either).
• tests/agent/test_zero_tests_is_not_green.py gains TheFinishGateIsToldTest: the reported file is refused by the finish gate, a real TestCase still finishes, and the refusal is checked against what discovery actually collects for five file shapes (orphan method, import only, plain class, real TestCase, subclass of a local TestCase).
• tests/scan/test_names.py had a fixture that wrote a module-level test method and asserted the oracle accepted it as coverage. It now writes a TestCase, which is what the rule always meant.

Verification

A reproducer rebuilds the project from the report in a temporary directory, runs discovery, then asks the finish gate for a verdict. Before the change it printed Ran 0 tests together with an empty refuse_done, and exited 1 with BUG REPRODUCED on 3 of 3 runs. After the change, on 3 of 3 runs it prints the same Ran 0 tests and the gate answers no test calls apply_discount. Action: patch Path: tests/test_module.py Append: one AAA test that calls apply_discount., exiting 0 with FIXED.

The three new regression tests fail on the base revision (FAILED (failures=3)) and pass after it. The full suite is green on both: python -m unittest discover -s tests -q reports OK (skipped=1) with 1132 tests after the change (1129 on the base revision).

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Automated contribution. This pull request was prepared by Squasher, an automated agent that reproduces a reported defect in a sandbox before proposing a fix. A human reviewed and approved this patch before it was opened.

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