test(consumer): fix TransactionManager stop/start-transaction assertions

[wbarnha]

Description

Re-enables TestTransactionManager::test__stop_transactions and test_start_transactions, skipped "Needs fixing".

Both used assert_called_once_with([call("0-0"), call("1-0")]) — which asserts a single producer call whose only argument is a list of Call objects. That's not what the code does: _stop_transactions / _start_transactions drive the producer once per transaction id (stop_transaction / maybe_begin_transaction, each with a single string arg), so for two ids there are two calls (the original even had commented-out notes about "extra garbage" calls it couldn't reconcile).

Fix (test-only): assert it faithfully — assert_has_calls([call("0-0"), call("1-0")], any_order=True) plus call_count == 2. Ordering isn't asserted because the ids come from a set and traced_from_parent_span interleaves shortlabel mock accesses between the two real calls. Only the Kafka producer is mocked; the manager logic runs for real.

Verification

tests/unit/transport/test_consumer.py → 115 passed; flake8/black/isort clean. Produced under adversarial faithfulness review (confirmed the old assertion was genuinely broken and the new one reflects real behaviour).

🤖 Generated with Claude Code

---

Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.25%. Comparing base (f77a678) to head (5456102).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #722      +/-   ##
==========================================
+ Coverage   94.18%   94.25%   +0.07%     
==========================================
  Files         104      104              
  Lines       11154    11154              
  Branches     1202     1202              
==========================================
+ Hits        10505    10513       +8     
+ Misses        548      540       -8     
  Partials      101      101              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.