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A pytest plugin to trace resource leaks.

Project description

pytest-leaks - A pytest plugin to trace resource leaks

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A pytest plugin to trace resource leaks.


  -R LEAKS, --leaks=LEAKS
                        runs each test several times and examines
                        sys.gettotalrefcount() to see if the test appears to
                        be leaking references. The argument should be of the
                        form stab:run where 'stab' is the number of times the
                        test is run to let gettotalrefcount settle down, 'run'
                        is the number of times further it is run. These
                        parameters all have defaults (5 and 4, respectively),
                        and the minimal invocation is '-R :'.

To add a leaks test to your py.test session, add the -R option on the command line:

$ python3-debug -mpytest -v -R : examples/
=========================== test session starts ===========================
platform linux -- Python 3.7.5, pytest-5.3.1, py-1.8.0, pluggy-0.13.1 -- .
cachedir: .pytest_cache
rootdir: .
plugins: leaks-0.3.1
collected 4 items

examples/ LEAKED                   [ 25%]
examples/ FAILED                  [ 50%]
examples/ PASSED                  [ 75%]
examples/ LEAKED            [100%]

================================ FAILURES =================================
___________________________ test_broken_faucet ____________________________

    def test_broken_faucet():
>       assert 0
E       assert 0

examples/ AssertionError
============================== leaks summary ==============================
examples/ leaked references: [2, 2, 2, 2], memory blocks: [2, 2, 2, 2]
examples/ leaked (not checked): 'not testing'
================== 1 failed, 1 passed, 2 leaked in 0.50s ==================

Note that a debug build of Python must be used. The test file used above contains the following code:

$ cat
import pytest

drops = []
def test_leaky_faucet():

def test_broken_faucet():
    assert 0

def test_mended_faucet():
    assert 1

@pytest.mark.no_leak_check(fail=True, reason="not testing")
def test_skip_marker_example():

Note that pytest-leaks runs tests several times: if you see test failures that are present only when using pytest-leaks, check that the test does not modify any global state in a way that prevents it from running a second time.


  • Detects memory leaks by running py.test tests repeatedly and comparing total reference counts between the runs.


  • py.test version >= 3;
  • A debug build of Python (2.7 or >=3.5).

On Linux, Python debug builds can be found in packages pythonX.Y-dbg (Debian and derivatives) and python3-debug (Fedora and derivatives).


You can install "pytest-leaks" via pip from PyPI:

$ pip install pytest-leaks


Contributions are very welcome. Tests can be run with tox, please ensure the coverage at least stays the same before you submit a pull request.


Distributed under the terms of the MIT and PSF licenses, "pytest-leaks" is free and open source software.


If you encounter any problems, please file an issue along with a detailed description.

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