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pytest-fail-slow is a pytest plugin for treating tests as failed if they took too long to run. It adds markers for failing tests if they or their setup stages run for longer than a given duration, along with command-line options for applying the same cutoff to all tests.

Note that slow tests will still be run to completion; if you want them to instead be stopped early, use pytest-timeout.

pytest-fail-slow requires Python 3.8 or higher and pytest 7.0 or higher. Just use pip for Python 3 (You have pip, right?) to install it:

python3 -m pip install pytest-fail-slow

To cause a specific test to fail if it takes too long to run, apply the fail_slow marker to it, with the desired cutoff time as the argument:

import pytest

@pytest.mark.fail_slow("5s")
def test_something_sluggish():
    ...

In addition, the --fail-slow DURATION option can be passed to the pytest command to affect all tests in that run. If --fail-slow is given and a test has the fail_slow marker, the duration given by the marker takes precedence for that test.

If a test fails due to being slow, pytest's output will include the test's duration and the duration threshold, like so:

________________________________ test_func ________________________________
Test passed but took too long to run: Duration 123.0s > 5.0s

Note: This feature only takes the durations for tests themselves into consideration. If a test passes in less than the specified duration, but one or more fixture setups/teardowns take longer than the duration, the test will still be marked as passing. To fail a test if the setup takes too long, see below.

New in version 0.4.0

To cause a specific test to fail if the setup steps for all of its fixtures combined take too long to run, apply the fail_slow_setup marker to it, with the desired cutoff time as the argument:

import pytest

@pytest.mark.fail_slow_setup("5s")
def test_costly_resource(slow_to_create):
    ...

Do not apply the marker to the test's fixtures; markers have no effect on fixtures.

In addition, the --fail-slow-setup DURATION option can be passed to the pytest command to affect all tests in that run. If --fail-slow-setup is given and a test has the fail_slow_setup marker, the duration given by the marker takes precedence for that test.

If the setup for a test takes too long to run, the test will be marked as "errored," the test itself will not be run, and pytest's output will include the setup stage's duration and the duration threshold, like so:

_______________________ ERROR at setup of test_func _______________________
Setup passed but took too long to run: Duration 123.0s > 5.0s

Note: If a test depends on multiple fixtures and just one of them exceeds the given duration on its own, the remaining fixtures will still have their setup steps run. Also, all fixture teardowns will still be run after the test would have run.

A duration passed to a marker or command-line option can be either a bare number of seconds or else a floating-point number followed by one of the following units (case insensitive):

• h, hour, hours
• m, min, mins, minute, minutes
• s, sec, secs, second, seconds
• ms, milli, millisec, milliseconds
• us, μs, micro, microsec, microseconds