[dmccoystephenson]

Summary

Stage B (unit-test expansion) cycle, scoped to the installation-ID file path. Characterization tests only; no production code changed.

• test_install_id_file_accepts_a_path_object — install_id_file= and TraceClient.install_id_from_file are both annotated Union[str, os.PathLike[str]], but every existing test passed a str. The new test passes a pathlib.Path (with a parent directory that does not exist yet) and checks that the ID is written, read back, used by the constructor, and sent as the install tag.
• test_install_id_from_file_writes_an_id_into_an_existing_empty_file — the branch where the file exists but holds no lines had no test. The test checks that a fresh UUID is written into it.

No tracking issue — gap found during triage.

Skipped issues

• The version tag is added even when it pushes an event past MAX_TAGS #16 (version tag can push an event past MAX_TAGS) was deferred: the issue says the fix is Java-visible and has to be decided together with trace-client-java, so it can't be changed from the Python side alone.

Java parity

No Java-visible behavior changed (tests only).

Test plan

• python3 -m unittest -v locally on Python 3.8.10: Ran 56 tests, OK
• CI test (3.8), test (3.10), test (3.12) green

This PR description was drafted during a Gardener session (https://github.com/Stephenson-Software/gardener).

🤖 Generated with Claude Code

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drafted by Claude on behalf of Daniel Stephenson

[dmccoystephenson]

Self-review rubric (PR #19):

• Scope: PASS — only tests/test_trace_client.py is modified (one import pathlib plus two tests); no production, doc or config file touched.
• Tests-new: PASS — no new public names; the two tests cover the os.PathLike half of the install_id_file/install_id_from_file signature and the existing-but-empty-file branch, neither of which had a test before.
• Tests-fix: N/A — characterization tests only, no bug fix in scope.
• Sibling structure: PASS — both tests sit in the per-installation-ID section of TraceClientTest, use _tmpdir()/_sent_tags(), and close the enabled client they build (via _sent_tags).
• Sibling renames: N/A — nothing renamed.
• Docs: PASS — tests only; README and docstrings already describe this behavior (Union[str, os.PathLike[str]], "does not exist or holds no such line").
• Issue resolution: N/A — no Closes; gap found during triage. The version tag is added even when it pushes an event past MAX_TAGS #16 deferred (needs a coordinated decision with trace-client-java).
• CI: PASS — test (3.8), test (3.10), test (3.12) all green on the PR head.
• Stdlib-only: PASS — the only added import is pathlib.
• Py3.8 floor: PASS — test (3.8) green; Path.read_text(encoding=) exists in 3.8. Ran locally on 3.8.10 as well: Ran 56 tests, OK.
• Never-raises / never-blocks, Log level, Version agreement, Exports: N/A — no production code changed.
• Java parity noted: PASS — the PR body says no Java-visible behavior changed.

Judgment note: tests/test_trace_client.py — open(path, "w", encoding="utf-8").close() creates the empty file without a with block. It is a one-line touch-and-close, so it was left as is. Neither test exercises the Pyodide path, which CI never runs anyway.

Summary: tests-only PR, anchor green, no do-not-auto-merge path touched — ready to merge.

This review comment was drafted during a Gardener session (https://github.com/Stephenson-Software/gardener).

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drafted by Claude on behalf of Daniel Stephenson