I am looking to parametrize a pytest function with the results from a fixture. Note: I do not want to parameterize with different fixtures as is often asked instead!
In essence, the parametrization is dependent on the test data which is read from a file that changes between test invocations.
import pytest
@pytest.fixture(scope='session')
def all_components():
# expensive fixture
# read from a file that changes between test invocations
# here hard-coded to illustrate structure
return [
{'name': 'ABC', 'type': 1, 'my_value': 'foo'},
{'name': 'DEF', 'type': 2, 'my_value': 'bar'},
# ...,
{'name': 'XYZ', 'type': 1, 'my_value': 'foobar'},
]
class TestSomething:
@pytest.fixture(scope='class')
def transformed_components(self, all_components):
# components are transformed
return all_components
@pytest.fixture(scope='session')
def filtered_component_names(self, transformed_components, request):
# extract some subset of data from the scenario definition
# contrived example for the sake of argument
return [val['name'] for val in transformed_components
if val['type'] == request.param]
@pytest.mark.parametrize('filtered_component_names', [1], scope='class', indirect=True)
@pytest.mark.parametrize('component_name', pytest.lazy_fixture('filtered_component_names'), scope='class')
class TestSubSomething:
@pytest.fixture(scope='class')
def get_value(self, transformed_components, component_name):
component_dict = {
comp['name']: comp
for comp in transformed_components
}
def get_value_impl(field):
# some calculation happens here
return component_dict[component_name][field]
return get_value_impl
def test_something1(self, get_value, component_name, filtered_component_names):
# details of the access is abstracted away,
# i.e. no need to specify component_name, etc.
assert get_value('my_value') == 'bar'
def test_somethin2(...):
...
@pytest.mark.parametrize('filtered_component_names', [2], scope='class', indirect=True)
@pytest.mark.parametrize('component_name', pytest.lazy_fixture('filtered_component_names'), scope='class')
class TestSubSomethingElse:
...
This almost works. The issue is that pytest.lazy_fixture is not iterable.
Also slightly ugly is that component_name, filtered_component_names must be passed to tests even though they are required only for the fixtures. But this I could live with.
Is there a way of actually making this work?
