my question is - is it possible to use return value from fixture as a value in parametrize? The problem is - I'd like to dynamically get possible values (for example, available systems on a virtual server) for parametrize. I can access these when a virtual server is created by one of the fixtures. Tests look like this (pseudo-code-ish):
[conftest.py]
@pytest_fixture(scope='session')
def test_server(request):
test_server = Server([default_params])
test_server.add()
def fin():
test_server.delete()
request_addfinalizer(fin)
return test_server()
[tests.py]
def test_basic_server(test_server):
systems = test.server.get_available_systems()
for system in systems:
test_server.install(system)
test_server.run_checks()
test_server.uninstall(system)
def test_other(test_server):
[other tests]
etc
This way, one server is added for each session, then all tests run on it, and after session ends, server is removed. But is there a way to get the available systems in @pytest.mark.parametrize without explicitly listing them (statically as a list in parametrize), using the method from server that is added when the session begins? That way each system would run in a separate test.
I tried using test_server in another fixture and then returning the list (the same way test_server is returned by test_server fixture, but I cannot use that as a value in parametrize - since decorator is evaluated before the test_server fixture is called in any test, and getting the list depends on test_server fixture.
This would be ideal:
[tests.py]
@pytest.mark.parametrize('system',[systems_list <- dynamically generated
when the server is created])
def test_basic_server(test_server,system):
test_server.install(system)
test_server.run_checks()
test_server.uninstall(system)
This is just a very basic example, in my tests I need to parametrize based on multiple scenarios and values and I end up with giant arrays when I do it statically.
But the principle remains the same - basically: can I call the fixture before the first test using this fixture runs, or how can pytest.mark.parametrize() access fixture values?
I think you may be unable to achieve what you want directly. Because @pytest.mark.parametrize
is being called during collecting, and fixtures will be called after collection completed.
But I have an alternative way to achieve similar result, mainly by extending pytest plugin pytest_generate_tests
and using method metafunc.parametrize
. https://pytest.org/latest/parametrize.html#basic-pytest-generate-tests-example
Here is my solution. In conftest.py
class System(object):
def __init__(self, name):
self.name = name
def __repr__(self):
return "<System '{}'>".format(self.name)
def get_available_systems():
return [System('A'), System('B'), System('C')]
def pytest_generate_tests(metafunc):
if 'system' in metafunc.fixturenames:
available_systems = get_available_systems()
metafunc.parametrize('system', available_systems)
In test file:
def test_basic_server(system):
print(system)
This is the output, you will have access to each system in test.
collected 3 items
test_01.py::test_basic_server[system0] <System 'A'>
PASSED
test_01.py::test_basic_server[system1] <System 'B'>
PASSED
test_01.py::test_basic_server[system2] <System 'C'>
PASSED
The bad thing is, get_available_systems
will be called every time whenever using fixture system
, which is not what you want. But I think it's not hard to add some extra logic to make the query logic only be executed once.
For example:
def pytest_generate_tests(metafunc):
if 'system' in metafunc.fixturenames:
if hasattr(metafunc.config, 'available_systems'):
available_systems = metafunc.config.available_systems
else:
available_systems = get_available_systems()
metafunc.config.available_systems = available_systems
metafunc.parametrize('system', available_systems)
I was able to work a similar problem where I have to generate tests data that is to be used for parameterization on the fly:
class TestFilters(object):
cls_testdata1 = []
def setup_class(cls):
r = []
for i in range(5):
r.append((x, y, z))
TestFilters.cls_testdata1 = r
@pytest.mark.parametrize("filter_id", list(range(5)))
def test_func(self, filter_id):
params = TestFilters.cls_testdata1[filter_id]
...
This would support adding the parameters dynamically, only that you need to predetermine the number of tests.
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