Three repr tests assert nothing; wait_incrementing's max cap and the idle_for statistic have no test that pins them

While running a mutation-based check of the test suite at 3e58094 a few gaps came up that seemed worth a note. None of this is a bug in tenacity — every "break" below was deliberate, and the shipped code is correct. The core is well guarded: flipping the stop_after_attempt boundary reddened 28 tests, disabling retry_if_exception_type 36, reraise=True 8, the attempt_number statistic 12.

1. repr tests that cannot fail

TestBase::test_retrying_repr, test_asyncio.py::TestAsyncio::test_repr and test_tornado.py::TestTornado::test_repr each call repr(...) and assert nothing. With BaseRetrying.__repr__ changed to return "" all three still pass. They do catch a repr that raises, but not one that is wrong. test_callstate_repr two lines below the first one asserts on the string and is the shape these could take.

2. wait_incrementing's max is never exercised

The only test (test_incrementing_sleep) passes no max. Removing the cap — max(0, min(result, self.max)) → max(0, result) — survives the suite. With max=3 the strategy should return [1, 2, 3, 3, 3, 3] across attempts 1–6; the mutant returns [1, 2, 3, 4, 5, 6]. One extra case with max= and an attempt past it would cover it.

3. statistics["idle_for"] is only ever asserted with mock.ANY

All four assertions on the statistics dict use "idle_for": mock.ANY, so never accumulating it (self.statistics["idle_for"] += sleep → pass) survives. In those tests the wait is fixed, so the expected total is known and could be pinned.

4. Two tests with no possible red

test_legacy_explicit_stop_type and test_legacy_explicit_wait_type construct Retrying(stop="stop_after_attempt") / Retrying(wait="exponential_sleep") (with a type: ignore) and assert nothing. There is no string-handling code in BaseRetrying.__init__ to break, so the tests can only fail if the constructor starts rejecting strings. If legacy string support was removed at some point, these may be leftovers.

Full write-up with the mutation spec and per-test results, reproducible against 3e58094: https://github.com/ArnauFerma/falsifiable-tests/blob/main/case-studies/tenacity.md

Happy to send a PR for 1–3 if you'd like one.