How to get coverage reporting when testing an Ansible lookup plugin

[andy-maier]

I am developing an Ansible lookup plugin and test code for it. Both the lookup plugin and the test code for the plugin work fine.

I am using "pytest" with "pytest-ansible" for that test, and the test function uses the ansible_module fixture provided by "pytest-ansible" to invoke the builtin "set_fact" module to invoke the lookup. The test function looks like this (simplified):

import pytest

@pytest.mark.ansible(host_pattern='localhost', connection='local')
def test_mylookup(ansible_module):
    expr = "lookup('myorg.mycoll.mylookup', 'someterm')"   # Jinja2 expression to call the lookup to be tested
    contacted = ansible_module.set_fact(result=f"{{{{ {expr} }}}}")    # Call the lookup
    contacted_host = contacted['localhost']
    result = contacted_host['ansible_facts']['result']   # result value returned by the lookup
    # ... assertions on result

Again, this all works fine. The problem is that this test does not add to the test coverage (0%). Other Python modules in my project do add to the test coverage, just the tests for Ansible plugins do not.

I suppose this is because the ansible_module object at some point uses Ansible mechanisms to execute the module, and that probably lets my lookup code run in a different thread or process. But this is speculation.

I am using the "pytest-cov" and "coverage" packages to have "pytest" count the coverage, and run the test by invoking pytest with --cov* options.

Relevant Python package versions (on Python 3.9):

ansible                   8.7.0
ansible-core              2.15.13
pytest                    7.4.4
pytest-ansible            4.1.1
pytest-cov                6.0.0
coverage                  7.6.4

I would like to know how I can get the test coverage properly accounted for when testing an Ansible lookup plugin with "pytest" and "pytest-ansible".

I also posted this question on SO: https://stackoverflow.com/q/79174901/1424462