Marien Zwart said

Because of the place option parsing happens pytest relies on there
being exactly one directory called "test" or "tests" somewhere below
the current directory. The "pytest" main script walks down from the
current directory and calls testlib.main on every directory called
test or tests it finds. This main function then (re)parses the
arguments and runs the tests. This is especially annoying for --help
(which does nothing if there is no test or tests dir below the current
one) or -t (specify testdir explicitly, which does nothing if there is
no test or tests dir below the current one and runs the tests more
than once if there is more than one).