ci(tests): run the test suite on windows-latest

[rboni-dk]

CI has never run a test on Windows, which is where the installer's pip path fails silently. This runs the existing suite on windows-latest for every PR — about 90 seconds, covering the bug classes that need no real install: encodings, path handling, and the platform branches themselves.

The suite could not run there at all. conftest's autouse _no_real_process_group_signals patches os.killpg and os.getpgid, neither of which exists on Windows, so all 255 tests errored before executing. That guard exists to stop a Popen-mocked test from signalling a real process group; where there are no process groups there is nothing to guard, so it now steps aside. Seven tests in test_tg_start.py patch os.killpg themselves to assert on the POSIX stop path — those are marked posix_only and skipped, since supports_graceful_stop() keeps the installer off that branch on Windows entirely. 248 of 255 run there.

Shimming them instead would have been an active trap: the natural refactor of supports_graceful_stop() is a capability check, and a synthetic signal.SIGKILL would make it report True on Windows and send those tests quietly down the POSIX branch.

It found a real defect

stream_iterator wrapped its buffer in a TextIOWrapper with no encoding, so command output was decoded with locale.getpreferredencoding() — cp1252 on US Windows. That mangles the box-drawing characters and check marks docker compose and uv draw progress with, and silently defeats the partial-character handling immediately below it: the loop breaks on UnicodeDecodeError to wait for the rest of an incomplete UTF-8 sequence, but cp1252 maps almost any byte to something, so the sequence decodes to garbage instead of raising.

test_stream_iterator has covered this all along — it had just never run anywhere the locale encoding was not UTF-8. Reproducible on any host:

LC_ALL=en_NZ.ISO8859-1 pytest tests/test_stream_iterator.py

Tests that were platform-dependent by accident

Five were found locally by forcing platform.system() to "Windows", two more by the first real run. Each now pins the platform it actually tests rather than inheriting the host's.

The notable pair is test_obs_existing_install_abort and test_tg_existing_install_abort, which built a JSON payload by interpolating a path. On Windows that path carries backslashes — invalid escapes — so the payload failed to parse, the step found no existing install, and never aborted. Both now build it through json.dumps, as docker compose ls --format json emits it.

test_stop_app_tree_no_op_when_proc_already_exited also gains a docstring: it encodes a shortcut Windows deliberately does not take, so nobody later "fixes" it by making Windows no-op again.

Notes

The job is separate rather than a matrix leg on test: both legs would upload an artifact named pytest-results, which upload-artifact@v4 rejects, and the coverage comment should come from one leg only. tests/installer.py is a symlink, which a Windows checkout may materialize as a plain file holding the target path — the job copies over it when that is what it got, and leaves a real link alone.

Run tests on Windows needs adding to the required checks before it gates merges.

🤖 Generated with Claude Code

[github-actions]

Coverage Report •

File	Stmts	Miss	Cover	Missing
dk-installer.py	1932	425	78%	159–160, 164–165, 177–189, 217–218, 221, 226–230, 240–241, 250–262, 267, 280, 326–327, 391, 431–438, 445, 457, 479–480, 529, 579–582, 601–602, 604, 654–683, 687–724, 755–773, 844, 915–916, 984, 1001–1002, 1019–1024, 1098–1099, 1109, 1125–1129, 1132, 1135, 1138, 1149–1182, 1291, 1297, 1343, 1346, 1353–1354, 1360–1362, 1462–1473, 1522–1537, 1540–1551, 1568–1569, 1606–1607, 1633–1634, 1641, 1646, 1652–1653, 1686–1689, 1698–1699, 1704–1705, 1721–1732, 1778–1780, 1990–2029, 2070–2073, 2165–2168, 2205, 2234, 2259–2261, 2269–2271, 2329, 2331, 2333, 2448–2449, 2467, 2497, 2506, 2509–2511, 2554–2566, 2571–2578, 2586–2596, 2745–2758, 2792–2793, 2833–2834, 2848, 2907, 2926–2927, 3106–3176, 3179–3181, 3184–3186, 3257, 3300–3318, 3322, 3327, 3379–3381, 3384–3386, 3412–3415, 3434–3450, 3453–3455, 3458–3460, 3487–3492, 3587–3595, 3598–3600, 3608–3612, 3676–3678, 3685–3687, 3698–3701, 3706–3707, 3713–3714, 3725–3734, 3743–3797, 3801–3837, 3841–3856
TOTAL	1932	425	78%

Tests	Skipped	Failures	Errors	Time
255	0 💤	0 ❌	0 🔥	2.249s ⏱️

[aarthy-dk]

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