Tests using the same machine-wide resource should not run in parallel

Feature or enhancement

Some resources which tests use are not per-process: the display, the sound device, the terminal. Two tests using one of them at the same time can interfere with each other, and regrtest runs test files in parallel by default.

Only tests using the same resource conflict. A GUI test can run in parallel with any non-GUI test, so pausing all the other tests would be too much.

These resources are already named on the command line: gui, audio, console and curses. A test declares which one it needs with requires(), requires_resource() or, for the memory, bigmemtest(), so those functions could lock the resource for the duration of the test or of the test file. The ~50 GUI modules, test_winsound, test_curses, test_winconsoleio and the bigmem tests would need no change.

The cost is that such tests no longer overlap each other: running test_tkinter, test_ttk and test_idle with -j4 takes as long as all three together (7.1 s here) instead of as long as the slowest (3.5 s). Tests which use no such resource keep running in parallel with them.

Linked PRs

• gh-156902

Inizia con regrtest e le dichiarazioni delle risorse indicate nell’issue: requires(), requires_resource() e bigmemtest(). Esamina come i test GUI, audio, console, curses e bigmem dichiarano attualmente le risorse, quindi verifica che i test che condividono una risorsa non si sovrappongano più, mentre i test non correlati continuino a essere eseguiti in parallelo.