Example of a `pytest.indirect` fixture passing along its name ("a" or "b", as `request.param`) to look up values rather than parametrising directly in a decorator

indirect_fixture_enums_synced_test.py

from enum import Enum

from pytest import fixture, mark


class Int1(Enum):
    small = 0
    large = 100


class Int2(Enum):
    small = 2
    large = 200


@fixture(scope="function")
def numbers(request) -> tuple[int, int]:
    return Int1[request.param].value, Int2[request.param].value


@mark.parametrize("numbers,total", [("small", 2), ("large", 300)], indirect=["numbers"])
def test_other(numbers, total):
    "A fixture with an 'indirect' parameter, which passes along its name"
    first, second = numbers
    assert first + second == total

indirect_fixture_enums_test.py

from enum import Enum

from pytest import fixture, mark


class Int1(Enum):
    a = 0
    c = 1

class Int2(Enum):
    b = 2
    d = 2


@fixture(scope="function")
def first(request):
    return Int1[request.param].value


@fixture(scope="function")
def second(request):
    return Int2[request.param].value


@mark.parametrize(
    "first,second,total", [("a", "b", 2), ("c", "d", 3)], indirect=["first", "second"]
)
def test_other(first, second, total):
    "A fixture with an 'indirect' parameter, which passes along its name"
    assert first + second == total

indirect_fixture_test.py

from pytest import fixture, mark


def lookup_indirect(name) -> int:
    return {"a": 0, "b": 1}[name]


@fixture(scope="function")
def a(request):
    return lookup_indirect(name=request.param)


@fixture(scope="function")
def b(request):
    return lookup_indirect(name=request.param)


@mark.parametrize("a,b", [("a", "b")], indirect=["a", "b"])
def test_other(a, b):
    "A fixture with an 'indirect' parameter, which passes along its name"
    assert a == 0
    assert b == 1

Note: this shows how to parametrise with a fixture. You may instead want to parameterise the fixture (@pytest.fixture(params=[...]))

You could extend this to parametrize with a 2nd tuple ("c", "d"), and add entries in the lookup dict for keys c and d. This might be useful if you had a 3rd [non-indirect] parameter which these lookup values may relate to.

For example, you may have your keys be filenames used to look up file contents, and a 3rd value would be a result (e.g. a diff)