You most certainly know that you can run a single test in entire suite by passing the full path:
PRODUCT_ENV='stage' pytest -v --critical tests/test_mod.py::test_func[x1]
This gets old when you want to run around 3 or more tests. In that case, you might end up putting paths into a file and passing this file content as command arguments. You probably know that, too:
PRODUCT_ENV='stage' pytest -v --critical $(< /tmp/ci-failures.txt)
However, this will fail if your test has space in the name (probably as pytest parameter value). Shell still performs command arguments splitting on space.
To avoid this problem, use cat and xargs:
cat /tmp/ci-failures.txt |PRODUCT_ENV='stage' xargs -n 200 -d '\n' pytest -v --critical
I always thought that xargs runs the command for each line from stdin, so I would avoid it when command takes a long time to start. But turns out, xargs is a little more sophisticated - it can group input lines into subclasses and run a command once for each subclass.
-n 200 tells xargs to use no more than 200 items in subclass, effectively forcing it to run pytest command once. -d '\n' tells it to only delimit arguments on newline, removing any special meaning from space.
PRODUCT_ENV and any other environment variables must be set after the pipe character, or exported beforehand, because each part of shell pipeline is run in a separate subshell.
After writing this article, I learned that since pytest 8.2 (released in April 2024), you can achieve the same by asking pytest to parse a file for you:
PRODUCT_ENV='stage' pytest -v --critical @/tmp/ci-failures.txt
However, everything written above still stands for scenarios where any other shell command is used in place of pytest.
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