"Testing plugins" example doesn't work

[gsnedders]

Hello!

I'm trying to follow the example in https://docs.pytest.org/en/7.4.x/how-to/writing_plugins.html#testing-plugins, but I can't get it to work.

I have an empty __init__.py.

I have a conftest.py containing:

# content of conftest.py

pytest_plugins = ["pytester"]

I have a plugin.py containing:

import pytest


def pytest_addoption(parser):
    group = parser.getgroup("helloworld")
    group.addoption(
        "--name",
        action="store",
        dest="name",
        default="World",
        help='Default "name" for hello().',
    )


@pytest.fixture
def hello(request):
    name = request.config.getoption("name")

    def _hello(name=None):
        if not name:
            name = request.config.getoption("name")
        return f"Hello {name}!"

    return _hello

And a test_plugin.py containing:

def test_hello(pytester):
    """Make sure that our plugin works."""

    # create a temporary conftest.py file
    pytester.makeconftest(
        """
        import pytest

        @pytest.fixture(params=[
            "Brianna",
            "Andreas",
            "Floris",
        ])
        def name(request):
            return request.param
    """
    )

    # create a temporary pytest test file
    pytester.makepyfile(
        """
        def test_hello_default(hello):
            assert hello() == "Hello World!"

        def test_hello_name(hello, name):
            assert hello(name) == "Hello {0}!".format(name)
    """
    )

    # run all tests with pytest
    result = pytester.runpytest()

    # check that all 4 tests passed
    result.assert_outcomes(passed=4)

(This is all exactly copy/pasted from the docs.)

Invoking pytest test_plugin.py leads to a bunch of captured stdout like:

/private/var/folders/qk/hmjj9_lx2cg3_4v3vx3y7y_w0000gn/T/pytest-of-gsnedders/pytest-23/test_hello0/test_hello.py:4
__________________ ERROR at setup of test_hello_name[Andreas] __________________
file /private/var/folders/qk/hmjj9_lx2cg3_4v3vx3y7y_w0000gn/T/pytest-of-gsnedders/pytest-23/test_hello0/test_hello.py, line 4
  def test_hello_name(hello, name):
E       fixture 'hello' not found
>       available fixtures: cache, capfd, capfdbinary, caplog, capsys, capsysbinary, doctest_namespace, monkeypatch, name, pytestconfig, record_property, record_testsuite_property, record_xml_attribute, recwarn, tmp_path, tmp_path_factory, tmpdir, tmpdir_factory
>       use 'pytest --fixtures [testpath]' for help on them.

…which makes me think it isn't loading the plugin? And, okay, I haven't installed it, so it isn't registered as an entry point. But adding pytester.plugins = ["plugin"] doesn't make it work, despite plugin being importable.

What am I doing wrong, and what do I need to do to make the example work preferably without making it installable?

[RonnyPfannschmidt]

Pytester is unable to discover local plugins when testing in a tmpdir

If the contest is not part of the collection tree it's simply never scanned by the nested pytest

The recommended way to test packaged Plugins is to have a editable install and using the entry point