Test coverage

Test coverage is somewhat spotty right now. Plenty of the core pieces are covered, along with actual bugs that were discovered by usage, but there are plenty of obvious gaps in our current verification.

Any contribution to increase coverage of the pytest tests is welcome.

Note that these tests do not have a usable py command, and so need to be structured to not rely on that - plenty of mocks, monkey-patching and directly importing commands is intended!

(For tests that can only be run after the full app is compiled/installed, create a new issue describing the scenario and why you think it wouldn't be valid as a unit test.)

首先檢查現有的 pytest 測試套件，並找出一個尚未涵蓋且可進行單元測試的核心區域；該 issue 未指定特定檔案或進入點。在不依賴可用的 py 指令的情況下組織測試，並視需要使用 mock、monkey-patching 或直接匯入指令。完成的標準是：針對選定的缺口新增有焦點的涵蓋範圍，並在不編譯或安裝完整應用程式的情況下維持測試有效。