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Pytest-example: specifying and selecting acceptance tests

# ./conftest.py
def pytest_option(parser):
    group = parser.getgroup("myproject")
    group.addoption(
        "-A", dest="acceptance", action="store_true", help="run (slow) acceptance tests"
    )


def pytest_funcarg__accept(request):
    return AcceptFixture(request)


class AcceptFixture:
    def __init__(self, request):
        if not request.config.getoption("acceptance"):
            pytest.skip("specify -A to run acceptance tests")
        self.tmpdir = request.config.mktemp(request.function.__name__, numbered=True)

    def run(self, *cmd):
        """ called by test code to execute an acceptance test. """
        self.tmpdir.chdir()
        return subprocess.check_output(cmd).decode()

and the actual test function example:

def test_some_acceptance_aspect(accept):
    accept.tmpdir.mkdir("somesub")
    result = accept.run("ls", "-la")
    assert "somesub" in result

If you run this test without specifying a command line option the test
will get skipped with an appropriate message. Otherwise you can start to
add convenience and test support methods to your AcceptFixture and drive
running of tools or applications and provide ways to do assertions about
the output.

example: decorating a funcarg in a test module {#decorate a funcarg}

For larger scale setups it’s sometimes useful to decorate a funcarg
just for a particular test module. We can extend the [accept
example](#accept example) by putting this in our test module:

def pytest_funcarg__accept(request):
    # call the next factory (living in our conftest.py)
    arg = request.getfuncargvalue("accept")
    # create a special layout in our tempdir
    arg.tmpdir.mkdir("special")
    return arg


class TestSpecialAcceptance:
    def test_sometest(self, accept):
        assert accept.tmpdir.join("special").check()

Our module level factory will be invoked first and it can ask its
request object to call the next factory and then decorate its result.
This mechanism allows us to stay ignorant of how/where the function
argument is provided -in our example from a conftest
plugin
.

sidenote: the temporary directory used here are instances of the
py.path.local class which provides many of the
os.path methods in a convenient way.