pytest - helper function or fixture, parametrization

Question

pytest setup is mostly based on fixtures and I like this approach because it's more atomic, explicit and less limiting that class inheritance in xUnit. Is there any convention or guideline to make fixtures instead helper functions?¹ Consider the code:

def create_flavored_cake(flavor):
    return Cake(flavor)

def test_chocolate():
    cake = create_flavored_cake('chocolate')
    assert cake.is_yummy()

def test_broccoli():
    cake = create_flavored_cake('broccoli')
    assert cake.is_yummy()

def test_broccoli_with_risins():
    cake = create_flavored_cake('broccoli')
    cake.add('risins')
    assert cake.is_yummy()

Should create_flavored_cake be transformed to a fixture?² Does such scenario, where tests have identical statements but different parameters, should trigger me to transform helper function to fixture to allow easier parametrization and reduce duplication?³ Should I use fixtures only for setup and teardown?⁴ Or it doesn't matter and by convention, if any, it should use fixture from the start?⁵

I don't really like parametrizing fixtures by indirect, but it seems there is not better way. Is that because it's a bad practice?⁶ I'm aware that I can also use pytest.mark.parametrize which will look better IMO. So where I should draw the lines between using fixture, helper function and some other approach (if there is a better solution) also taking into consideration parametrizing them?⁷

I've added superscripts for question reference. You don't have to give anwsers to all of them.

Answer 1

In the case that I have to do this, I just create a fixture that returns my function. I agree that the indirect method just seems to create ugly code.

@pytest.fixture
def generate_data():
    def generate_data_function(some_parameters):
        # Code goes here
    return generate_data_function

def test_something(generate_data):
    my_test_parameters = # something
    generate_data(my_test_parameters)

    # Do test...

As far as good practice goes, at least this way I can quickly see if a test is using a helper function, rather than importing it from a module for the whole file and only using it in some tests.