Why do hooks in plugins loaded through the INI file not fire, but they do when loaded through pytest.main()?

[dgard1981]

I have written a basic plugin that I wish to include via the INI file, but it doesn't seem to work. To demonstrate, take the example files below, which includes a plugin with two hooks -

• pytest_assertion_pass - Simply add 1 to a count of passed assertions.
• pytest_terminal_summary - Add "x assertions passed." to the end of the terminal summary.

It is possible to prove that the plugin is being loaded through the INI file because either -

• If the path is mis-typed then an import error occurs and pytest fails. or;
• If the plugin is include both in the INI file and through a pytest.main() call in code, a warning is displayed.

  PytestAssertRewriteWarning: Module already imported so cannot be rewritten: plugins.count_assertions

Now using the example files with the plugin loaded through the INI file, notice how the plugin hooks are not fired (x assertions passed. is not displayed in the terminal summary).

user@computer:~/plugin-test$ python src
.                                                                                                                                                                                            [100%]
1 passed in 0.00s
user@computer:~/plugin-test$ pytest src -q
.                                                                                                                                                                                            [100%]
1 passed in 0.00s

Finally, to show that the plugin works, updating the pytest.ini and __main__.py like the example files with the plugin loaded through code, notice how the plugin hooks are fired as expected.

user@computer:~/plugin-test$ python src
.                                                                                                                                                                                            [100%]
2 assertions passed.
1 passed in 0.00s

So my question is, how can do you get plugins to work through the INI file? It's not practical to assume that a pytest run will be started through code every time, and one must assume that the CLI will be used more often than not.

---

Example files - Plugin loaded through INI file

src/pytest.ini

[pytest]
addopts = -p src.plugins.count_assertions
enable_assertion_pass_hook = true

src/__main__.ini

import pytest

args = ['src', '-q']
pytest.main(args)

src/test_somthing.ini

def test_stdout():
    assert 1 == 1
    assert 2 == 2

src/plugins/count_assertions.py

class PassedAssertions:

    count = 0

    def pytest_assertion_pass(self, *_) -> None:
        self.count += 1

    def pytest_terminal_summary(self, *_) -> dict:
        print(f'{self.count} assertions passed.')

---

Example files - Plugin loaded through code

src/pytest.ini

[pytest]
enable_assertion_pass_hook = true

src/__main__.ini

from src.plugins.count_assertions import PassedAssertions
import pytest

args = ['src', '-q']
pytest.main(args, plugins=[PassedAssertions()])

[dgard1981]

To add a little more information... if the plugin was updated as follows, Module loaded is printed regardless of how the plugin is included.

However, Plugin initialised is only printed if the plugin is loaded through code - pytest.main(args, plugins=[PassedAssertions()])

So it seems that when including a plugin through the INI file, pytest doesn't look for and instantiate classes (which makes sense).

But manually instantiating the plugin class either in the plugin file or through __init__.py in the plugin directory also fails. Even though in both of those cases Plugin initialised is printed, presumably instantiation takes place too late.

print('Module loaded')
class PassedAssertions:

    count = 0

    def __init__(self) -> None:
        print('Plugin initialised')

    def pytest_assertion_pass(self, *_) -> None:
        self.count += 1

    def pytest_terminal_summary(self, *_) -> dict:
        print(f'{self.count} assertions passed.')

[RonnyPfannschmidt]

You would need a pytest-configure hook to make and register a instance

[dgard1981]

Forgive my ignorance, but how would I do that?

Using the below, my plugin is instantiated, but the hooks within are still not fired.

def pytest_configure(*_) -> None:
    p = PassedAssertions()

[RonnyPfannschmidt]

Registration with the plugin manager missing

See the builtin junitxml plugin for a example

[dgard1981]

Thanks for the pointer.

Both of these seem to work, so no I'm just trying to find some reading on config.stash to see if it's relevant for my use case.

def pytest_configure(config) -> None:
    config.stash['pytest_assertions_plugin'] = PytestAssertionsPlugin()
    config.pluginmanager.register(config.stash['pytest_assertions_plugin'])

def pytest_configure(config) -> None:
    config.pluginmanager.register(PytestAssertionsPlugin())

[RonnyPfannschmidt]

The stash is for accessing objects You put there, if the plugin class is self contained it's not necessary