pytest inline fixtures

pytest_inline_fixtures.py

from inspect import isfunction, signature, Parameter

import pytest


def make_fixture(value, scope='function'):
    if isfunction(value):
        sig = signature(value)
        if 'self' in sig.parameters:
            fixture = lambda self, **fxs: value(self, **fxs)   # noqa: E731
        else:
            fixture = lambda self=None, **fxs: value(**fxs)   # noqa: E731
            self_parameter = Parameter(
                name='self',
                kind=Parameter.POSITIONAL_ONLY,
                default=None,
            )
            new_parameters = [self_parameter, *sig.parameters.values()]
            sig = sig.replace(parameters=new_parameters)
        fixture.__signature__ = sig
    else:
        fixture = lambda self=None: value   # noqa: E731
    return pytest.fixture(scope=scope)(fixture)


foo = make_fixture('foo')
bar = make_fixture(lambda: 'bar')
foobar = make_fixture(lambda foo, bar: foo + bar)


def test(foo, bar, foobar):
    assert foo == 'foo'
    assert bar == 'bar'
    assert foobar == 'foobar'


class Test:

    value = '[self]'

    foo = make_fixture('FOO')
    bar = make_fixture(lambda: 'BAR')
    foobar = make_fixture(lambda foo, bar: foo + bar)
    selffoobar = make_fixture(lambda self, foo, bar: self.value + foo + bar)

    def test(self, foo, bar, foobar, selffoobar):
        assert foo == 'FOO'
        assert bar == 'BAR'
        assert foobar == 'FOOBAR'
        assert selffoobar == '[self]FOOBAR'