Usage

pytest-memray is a pytest plugin. It is enabled when you pass --memray to pytest:

$ python3.9 -m pytest tests/ --memray

Allocation tracking

By default, the plugin will track allocations in all tests. This information is reported after tests run ends:

.. example report starts

$ python3 -m pytest tests --memray
=============================== test session starts ================================
platform linux -- Python 3.8.10, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: /mypackage, configfile: pytest.ini
plugins: cov-2.12.0, memray-0.1.0
collected 21 items

tests/test_package.py .....................                                   [100%]


================================= MEMRAY REPORT ==================================
Allocations results for tests/test_package.py::some_test_that_allocates

     📦 Total memory allocated: 24.4MiB
     📏 Total allocations: 33929
     📊 Histogram of allocation sizes: |▂   █    |
     🥇 Biggest allocating functions:
        - parse:/opt/bb/lib/python3.8/ast.py:47 -> 3.0MiB
        - parse:/opt/bb/lib/python3.8/ast.py:47 -> 2.3MiB
        - _visit:/opt/bb/lib/python3.8/site-packages/astroid/transforms.py:62 -> 576.0KiB
        - parse:/opt/bb/lib/python3.8/ast.py:47 -> 517.6KiB
        - __init__:/opt/bb/lib/python3.8/site-packages/astroid/node_classes.py:1353 -> 512.0KiB

Markers

This plugin provides markers that can be used to enforce additional checks and validations on tests when this plugin is enabled.

Important

These markers do nothing when the plugin is not enabled.

limit_memory

When this marker is applied to a test, it will cause the test to fail if the execution of the test allocates more memory than allowed. It takes a single argument with a string indicating the maximum memory that the test can allocate.

The format for the string is <NUMBER> ([KMGTP]B|B). The marker will raise ValueError if the string format cannot be parsed correctly.

Warning

As the Python interpreter has its own object allocator is possible that memory is not immediately released to the system when objects are deleted, so tests using this marker may need to give some room to account for this.

Example of usage:

@pytest.mark.limit_memory("24 MB")
def test_foobar():
    # do some stuff that allocates memory

Fixtures

None provided at this time.