How to speed up pytest

Question

Is there some way to speed up the repeated execution of pytest? It seems to spend a lot of time collecting tests, even if I specify which files to execute on th

Answer 1

In bash, try { find -name '*_test.py'; find -name 'test_*.py'; } | xargs pytest.

For me, this brings total test time down to a fraction of a second.

Answer 2

In the special case where you are running under cygwin's python, its unix-style file handling is slow. See pytest.py test very slow startup in cygwin for how to speed things up in that special situation.

Answer 3

If you have some antivirus software running, try turning it off. I had this exact same problem. Collecting tests ran incredibly slow. It turned out to be my antivirus software (Avast) that was causing the problem. When I disabled the antivirus software, test collection ran about five times faster. I tested it several times, turning the antivirus on and off, so I have no doubt that was the cause in my case.

Edit: To be clear, I don't think antivirus should be turned off and left off. I just recommend turning it off temporarily to see if it is the source of the slow down. In my case, it was, so I looked for other antivirus solutions that didn't have the same issue.

Answer 4

Using the norecursedirs option in pytest.ini or tox.ini can save a lot of collection time, depending on what other files you have in your working directory. My collection time is roughly halved for a suite of 300 tests when I have that in place (0.34s vs 0.64s).

If you're already using tox like I am, you just need to add the following in your tox.ini:

[pytest]
norecursedirs = docs *.egg-info .git appdir .tox

You can also add it in a free-standing pytest.ini file.

The pytest documentation has more details on pytest configuration files.

Answer 5

With xdist you can parallelize pytest runs. It allows even to ship tests to remote machines. Depends on your setup it can speedup quite a bit :)

Answer 6

For me, adding PYTHONDONTWRITEBYTECODE=1 to my environment variables achieved a massive speedup! Note that I am using network drives which might be a factor.

• Windows Batch: set PYTHONDONTWRITEBYTECODE=1
• Unix: export PYTHONDONTWRITEBYTECODE=1
• subprocess.run: Add keyword env={'PYTHONDONTWRITEBYTECODE': '1'}
• PyCharm already set this variable automatically for me.

Note that the first two options only remain active for your current terminal session.