CODEWITHSUNDEEP
pythonunit-testingpytest
hardhypochondria
hardhypochondria

Reputation: 388

Pytest. Best way to define expected result when using stacked parametrize decorators?

I Have two similar testcases with each having more than 100 lines of code which creates aux objects for the test, those lines are very similar, in fact, only 2 lines differ between the tests setups and I wan't to get rid of the code repetition. I think that multiple parameterization might help me with this task. Using multiple parametrization I can combine setups in the one and actually provide better conditions for the test. Bun I can't wrap my head around of what is the best way to specify the expected result while using multiple parametrization when each combination will yield different results?

Consider this test case

@pytest.mark.parametrize('country', ['US', 'DE', 'FR', 'IT'])
@pytest.mark.parametrize('number', ['12345', '54321'])
def test_correct_record_is_selected_for_number(country, number):
    # 100 line long setup of different objects.
    record = get_record(country, number)
    assert record = expected_record

I expect that for a different combinations of (country, number) get_record function will return different results, and the only way I see to provide the expected result - is to reimplement the part of the get_record function logic in the test itself in order to determine which result to expect based on provided country and number, which doesn't seem right to me.

Is there a way to nicely specify expected output for stacked parametrize decorators? Or I'm better off with moving setup code to multiple different fixtures and leaving it as 2 separate tests that use different setup fixtures?

Upvotes: 4

Views: 4993

Answers (2)

MrBean Bremen
MrBean Bremen

Reputation: 16815

I'm not aware of a nice way, but in any case you have to list the different expected results somewhere. So you could just put them in a dictionary outside the test:

expected_record = {
    'US': {
        '12345': {...},
        '54321': {...},
    },
    'DE': {
        '12345': {...},
        '54321': {...},
    },
    ...
}

@pytest.mark.parametrize('country', ['US', 'DE', 'FR', 'IT'])
@pytest.mark.parametrize('number', ['12345', '54321'])
def test_correct_record_is_selected_for_number(country, number):
    record = get_record(country, number)
    assert record == expected_record[country][number]

Upvotes: 5

hoefling
hoefling

Reputation: 66261

Usually I put the results in a separate fixture that selects the expected value based on other arguments. Example:

expected_records = {'US': {'12345': 'fizz', '54321': 'buzz'}, 'DE': ...}


@pytest.fixture
def expected_record(request):
    country = request.node.funcargs['country']
    number = request.node.funcargs['number']
    return expected_records.get(country, dict()).get(number, None)


@pytest.mark.parametrize('country', ['US', 'DE', 'FR', 'IT'])
@pytest.mark.parametrize('number', ['12345', '54321'])
def test_correct_record_is_selected_for_number(country, number, expected_record):
    record = get_record(country, number)
    assert record == expected_record

However, in practice the data is rarely hardcoded in the script, so the logic of expected_record is usually data-driven, for example:

@pytest.fixture
def expected_record(request):
    country = request.node.funcargs['country']
    number = request.node.funcargs['number']
    file = pathlib.Path(request.config.rootdir, 'data', country).with_suffix('.json') # data/DE.json
    data = json.loads(file.read_text())  # {12345: "fizz", 54321: "buzz"}
    return data[number]

Upvotes: 7

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