pytest plugin

PyJulia automatically installs a pytest plugin. It takes care of tricky aspects of PyJulia initialization:

  • It loads libjulia as early as possible to avoid incompatibility of shared libraries such as libstdc++ (assuming that the ones bundled with julia are newer than the ones otherwise loaded).
  • It provides a way to succinctly mark certain tests require Julia runtime (see Fixture and Marker).
  • The tests requiring Julia can be skipped with --no-julia.
  • It enables debug-level logging. This is highly recommended especially in CI setting as miss-configuration of PyJulia may result in segmentation fault in which Python cannot provide useful traceback.

To activate PyJulia’s pytest plugin [1] add -p julia.pytestplugin to the command line option. There are several ways to do this by default in your project. One option is to include this using addopts setup of pytest.ini or tox.ini file. See How to change command line options defaults:

addopts =
    -p julia.pytestplugin
[1]This plugin is not activated by default (as in normal pytest-* plugin packages) to avoid accidentally breaking user’s pytest setup when PyJulia is included as a non-test dependency.


Following options can be passed to pytest


Skip tests that require julia.


Undo --no-julia; i.e., run tests that require julia.


Julia executable to be used. Defaults to environment variable PYJULIA_TEST_RUNTIME.


Some <julia_option> that can be passed to julia executable (e.g., --compiled-modules=no) can be passed to pytest plugin by --julia-<julia_option> (e.g., --julia-compiled-modules=no). See pytest -p julia.pytestplugin --help for the actual list of options.


PyJulia’s pytest plugin includes a pytest fixture julia which is set to an instance of Julia that is appropriately initialized. Example usage:

def test_eval(julia):
    assert julia.eval("1 + 1") == 2

This fixture also “marks” that this test requires a Julia runtime. Thus, the tests using julia fixture are not run when --no-julia is passed.


PyJulia’s pytest plugin also includes a pytest marker julia which can be used to mark that the test requires PyJulia setup. It is similar to julia fixture but it does not instantiate the actual Julia object.

Example usage:

import pytest

def test_import():
    from julia import MyModule