.. currentmodule:: _pytest.python
.. versionadded:: 2.0/2.3/2.4
The purpose of test fixtures is to provide a fixed baseline upon which tests can reliably and repeatedly execute. pytest fixtures offer dramatic improvements over the classic xUnit style of setup/teardown functions:
- fixtures have explicit names and are activated by declaring their use from test functions, modules, classes or whole projects.
- fixtures are implemented in a modular manner, as each fixture name triggers a fixture function which can itself use other fixtures.
- fixture management scales from simple unit to complex functional testing, allowing to parametrize fixtures and tests according to configuration and component options, or to re-use fixtures across class, module or whole test session scopes.
In addition, pytest continues to support :ref:`xunitsetup`. You can mix both styles, moving incrementally from classic to new style, as you prefer. You can also start out from existing :ref:`unittest.TestCase style <unittest.TestCase>` or :ref:`nose based <nosestyle>` projects.
Note
pytest-2.4 introduced an additional :ref:`yield fixture mechanism <yieldfixture>` for easier context manager integration and more linear writing of teardown code.
Test functions can receive fixture objects by naming them as an input argument. For each argument name, a fixture function with that name provides the fixture object. Fixture functions are registered by marking them with :py:func:`@pytest.fixture <_pytest.python.fixture>`. Let's look at a simple self-contained test module containing a fixture and a test function using it:
# content of ./test_smtpsimple.py
import pytest
@pytest.fixture
def smtp():
import smtplib
return smtplib.SMTP("smtp.gmail.com")
def test_ehlo(smtp):
response, msg = smtp.ehlo()
assert response == 250
assert 0 # for demo purposes
Here, the test_ehlo needs the smtp fixture value. pytest
will discover and call the :py:func:`@pytest.fixture <_pytest.python.fixture>`
marked smtp fixture function. Running the test looks like this:
$ py.test test_smtpsimple.py
======= test session starts ========
platform linux -- Python 3.5.1, pytest-2.9.2, py-1.4.31, pluggy-0.3.1
rootdir: $REGENDOC_TMPDIR, inifile:
collected 1 items
test_smtpsimple.py F
======= FAILURES ========
_______ test_ehlo ________
smtp = <smtplib.SMTP object at 0xdeadbeef>
def test_ehlo(smtp):
response, msg = smtp.ehlo()
assert response == 250
> assert 0 # for demo purposes
E assert 0
test_smtpsimple.py:11: AssertionError
======= 1 failed in 0.12 seconds ========
In the failure traceback we see that the test function was called with a
smtp argument, the smtplib.SMTP() instance created by the fixture
function. The test function fails on our deliberate assert 0. Here is
the exact protocol used by pytest to call the test function this way:
- pytest :ref:`finds <test discovery>` the
test_ehlobecause of thetest_prefix. The test function needs a function argument namedsmtp. A matching fixture function is discovered by looking for a fixture-marked function namedsmtp. smtp()is called to create an instance.test_ehlo(<SMTP instance>)is called and fails in the last line of the test function.
Note that if you misspell a function argument or want to use one that isn't available, you'll see an error with a list of available function arguments.
Note
You can always issue:
py.test --fixtures test_simplefactory.py
to see available fixtures.
In versions prior to 2.3 there was no @pytest.fixture marker
and you had to use a magic pytest_funcarg__NAME prefix
for the fixture factory. This remains and will remain supported
but is not anymore advertised as the primary means of declaring fixture
functions.
When injecting fixtures to test functions, pytest-2.0 introduced the term "funcargs" or "funcarg mechanism" which continues to be present also in docs today. It now refers to the specific case of injecting fixture values as arguments to test functions. With pytest-2.3 there are more possibilities to use fixtures but "funcargs" remain as the main way as they allow to directly state the dependencies of a test function.
As the following examples show in more detail, funcargs allow test functions to easily receive and work against specific pre-initialized application objects without having to care about import/setup/cleanup details. It's a prime example of dependency injection where fixture functions take the role of the injector and test functions are the consumers of fixture objects.
Fixtures requiring network access depend on connectivity and are
usually time-expensive to create. Extending the previous example, we
can add a scope='module' parameter to the
:py:func:`@pytest.fixture <_pytest.python.fixture>` invocation
to cause the decorated smtp fixture function to only be invoked once
per test module. Multiple test functions in a test module will thus
each receive the same smtp fixture instance. The next example puts
the fixture function into a separate conftest.py file so
that tests from multiple test modules in the directory can
access the fixture function:
# content of conftest.py
import pytest
import smtplib
@pytest.fixture(scope="module")
def smtp():
return smtplib.SMTP("smtp.gmail.com")
The name of the fixture again is smtp and you can access its result by
listing the name smtp as an input parameter in any test or fixture
function (in or below the directory where conftest.py is located):
# content of test_module.py
def test_ehlo(smtp):
response, msg = smtp.ehlo()
assert response == 250
assert b"smtp.gmail.com" in msg
assert 0 # for demo purposes
def test_noop(smtp):
response, msg = smtp.noop()
assert response == 250
assert 0 # for demo purposes
We deliberately insert failing assert 0 statements in order to
inspect what is going on and can now run the tests:
$ py.test test_module.py
======= test session starts ========
platform linux -- Python 3.5.1, pytest-2.9.2, py-1.4.31, pluggy-0.3.1
rootdir: $REGENDOC_TMPDIR, inifile:
collected 2 items
test_module.py FF
======= FAILURES ========
_______ test_ehlo ________
smtp = <smtplib.SMTP object at 0xdeadbeef>
def test_ehlo(smtp):
response, msg = smtp.ehlo()
assert response == 250
assert b"smtp.gmail.com" in msg
> assert 0 # for demo purposes
E assert 0
test_module.py:6: AssertionError
_______ test_noop ________
smtp = <smtplib.SMTP object at 0xdeadbeef>
def test_noop(smtp):
response, msg = smtp.noop()
assert response == 250
> assert 0 # for demo purposes
E assert 0
test_module.py:11: AssertionError
======= 2 failed in 0.12 seconds ========
You see the two assert 0 failing and more importantly you can also see
that the same (module-scoped) smtp object was passed into the two
test functions because pytest shows the incoming argument values in the
traceback. As a result, the two test functions using smtp run as
quick as a single one because they reuse the same instance.
If you decide that you rather want to have a session-scoped smtp
instance, you can simply declare it:
@pytest.fixture(scope="session")
def smtp(...):
# the returned fixture value will be shared for
# all tests needing itpytest supports execution of fixture specific finalization code
when the fixture goes out of scope. By accepting a request object
into your fixture function you can call its request.addfinalizer one
or multiple times:
# content of conftest.py
import smtplib
import pytest
@pytest.fixture(scope="module")
def smtp(request):
smtp = smtplib.SMTP("smtp.gmail.com")
def fin():
print ("teardown smtp")
smtp.close()
request.addfinalizer(fin)
return smtp # provide the fixture value
The fin function will execute when the last test using
the fixture in the module has finished execution.
Let's execute it:
$ py.test -s -q --tb=no FFteardown smtp 2 failed in 0.12 seconds
We see that the smtp instance is finalized after the two
tests finished execution. Note that if we decorated our fixture
function with scope='function' then fixture setup and cleanup would
occur around each single test. In either case the test
module itself does not need to change or know about these details
of fixture setup.
Another alternative to the request.addfinalizer() method is to use yield fixtures. All the code after the yield statement serves as the teardown code. See the :ref:`yield fixture documentation <yieldfixture>`.
Fixture function can accept the :py:class:`request <FixtureRequest>` object
to introspect the "requesting" test function, class or module context.
Further extending the previous smtp fixture example, let's
read an optional server URL from the test module which uses our fixture:
# content of conftest.py
import pytest
import smtplib
@pytest.fixture(scope="module")
def smtp(request):
server = getattr(request.module, "smtpserver", "smtp.gmail.com")
smtp = smtplib.SMTP(server)
def fin():
print ("finalizing %s (%s)" % (smtp, server))
smtp.close()
request.addfinalizer(fin)
return smtp
We use the request.module attribute to optionally obtain an
smtpserver attribute from the test module. If we just execute
again, nothing much has changed:
$ py.test -s -q --tb=no FFfinalizing <smtplib.SMTP object at 0xdeadbeef> (smtp.gmail.com) 2 failed in 0.12 seconds
Let's quickly create another test module that actually sets the server URL in its module namespace:
# content of test_anothersmtp.py
smtpserver = "mail.python.org" # will be read by smtp fixture
def test_showhelo(smtp):
assert 0, smtp.helo()
Running it:
$ py.test -qq --tb=short test_anothersmtp.py
F
======= FAILURES ========
_______ test_showhelo ________
test_anothersmtp.py:5: in test_showhelo
assert 0, smtp.helo()
E AssertionError: (250, b'mail.python.org')
E assert 0
voila! The smtp fixture function picked up our mail server name
from the module namespace.
Fixture functions can be parametrized in which case they will be called multiple times, each time executing the set of dependent tests, i. e. the tests that depend on this fixture. Test functions do usually not need to be aware of their re-running. Fixture parametrization helps to write exhaustive functional tests for components which themselves can be configured in multiple ways.
Extending the previous example, we can flag the fixture to create two
smtp fixture instances which will cause all tests using the fixture
to run twice. The fixture function gets access to each parameter
through the special :py:class:`request <FixtureRequest>` object:
# content of conftest.py
import pytest
import smtplib
@pytest.fixture(scope="module",
params=["smtp.gmail.com", "mail.python.org"])
def smtp(request):
smtp = smtplib.SMTP(request.param)
def fin():
print ("finalizing %s" % smtp)
smtp.close()
request.addfinalizer(fin)
return smtp
The main change is the declaration of params with
:py:func:`@pytest.fixture <_pytest.python.fixture>`, a list of values
for each of which the fixture function will execute and can access
a value via request.param. No test function code needs to change.
So let's just do another run:
$ py.test -q test_module.py
FFFF
======= FAILURES ========
_______ test_ehlo[smtp.gmail.com] ________
smtp = <smtplib.SMTP object at 0xdeadbeef>
def test_ehlo(smtp):
response, msg = smtp.ehlo()
assert response == 250
assert b"smtp.gmail.com" in msg
> assert 0 # for demo purposes
E assert 0
test_module.py:6: AssertionError
_______ test_noop[smtp.gmail.com] ________
smtp = <smtplib.SMTP object at 0xdeadbeef>
def test_noop(smtp):
response, msg = smtp.noop()
assert response == 250
> assert 0 # for demo purposes
E assert 0
test_module.py:11: AssertionError
_______ test_ehlo[mail.python.org] ________
smtp = <smtplib.SMTP object at 0xdeadbeef>
def test_ehlo(smtp):
response, msg = smtp.ehlo()
assert response == 250
> assert b"smtp.gmail.com" in msg
E assert b'smtp.gmail.com' in b'mail.python.org\nSIZE 51200000\nETRN\nSTARTTLS\nENHANCEDSTATUSCODES\n8BITMIME\nDSN\nSMTPUTF8'
test_module.py:5: AssertionError
-------------------------- Captured stdout setup ---------------------------
finalizing <smtplib.SMTP object at 0xdeadbeef>
_______ test_noop[mail.python.org] ________
smtp = <smtplib.SMTP object at 0xdeadbeef>
def test_noop(smtp):
response, msg = smtp.noop()
assert response == 250
> assert 0 # for demo purposes
E assert 0
test_module.py:11: AssertionError
4 failed in 0.12 seconds
We see that our two test functions each ran twice, against the different
smtp instances. Note also, that with the mail.python.org
connection the second test fails in test_ehlo because a
different server string is expected than what arrived.
pytest will build a string that is the test ID for each fixture value
in a parametrized fixture, e.g. test_ehlo[smtp.gmail.com] and
test_ehlo[mail.python.org] in the above examples. These IDs can
be used with -k to select specific cases to run, and they will
also identify the specific case when one is failing. Running pytest
with --collect-only will show the generated IDs.
Numbers, strings, booleans and None will have their usual string
representation used in the test ID. For other objects, pytest will
make a string based on the argument name. It is possible to customise
the string used in a test ID for a certain fixture value by using the
ids keyword argument:
# content of test_ids.py
import pytest
@pytest.fixture(params=[0, 1], ids=["spam", "ham"])
def a(request):
return request.param
def test_a(a):
pass
def idfn(fixture_value):
if fixture_value == 0:
return "eggs"
else:
return None
@pytest.fixture(params=[0, 1], ids=idfn)
def b(request):
return request.param
def test_b(b):
pass
The above shows how ids can be either a list of strings to use or
a function which will be called with the fixture value and then
has to return a string to use. In the latter case if the function
return None then pytest's auto-generated ID will be used.
Running the above tests results in the following test IDs being used:
$ py.test --collect-only ======= test session starts ======== platform linux -- Python 3.5.1, pytest-2.9.2, py-1.4.31, pluggy-0.3.1 rootdir: $REGENDOC_TMPDIR, inifile: collected 10 items <Module 'test_anothersmtp.py'> <Function 'test_showhelo[smtp.gmail.com]'> <Function 'test_showhelo[mail.python.org]'> <Module 'test_ids.py'> <Function 'test_a[spam]'> <Function 'test_a[ham]'> <Function 'test_b[eggs]'> <Function 'test_b[1]'> <Module 'test_module.py'> <Function 'test_ehlo[smtp.gmail.com]'> <Function 'test_noop[smtp.gmail.com]'> <Function 'test_ehlo[mail.python.org]'> <Function 'test_noop[mail.python.org]'> ======= no tests ran in 0.12 seconds ========
You can not only use fixtures in test functions but fixture functions
can use other fixtures themselves. This contributes to a modular design
of your fixtures and allows re-use of framework-specific fixtures across
many projects. As a simple example, we can extend the previous example
and instantiate an object app where we stick the already defined
smtp resource into it:
# content of test_appsetup.py
import pytest
class App:
def __init__(self, smtp):
self.smtp = smtp
@pytest.fixture(scope="module")
def app(smtp):
return App(smtp)
def test_smtp_exists(app):
assert app.smtp
Here we declare an app fixture which receives the previously defined
smtp fixture and instantiates an App object with it. Let's run it:
$ py.test -v test_appsetup.py ======= test session starts ======== platform linux -- Python 3.5.1, pytest-2.9.2, py-1.4.31, pluggy-0.3.1 -- $PYTHON_PREFIX/bin/python3.5 cachedir: .cache rootdir: $REGENDOC_TMPDIR, inifile: collecting ... collected 2 items test_appsetup.py::test_smtp_exists[smtp.gmail.com] PASSED test_appsetup.py::test_smtp_exists[mail.python.org] PASSED ======= 2 passed in 0.12 seconds ========
Due to the parametrization of smtp the test will run twice with two
different App instances and respective smtp servers. There is no
need for the app fixture to be aware of the smtp parametrization
as pytest will fully analyse the fixture dependency graph.
Note, that the app fixture has a scope of module and uses a
module-scoped smtp fixture. The example would still work if smtp
was cached on a session scope: it is fine for fixtures to use
"broader" scoped fixtures but not the other way round:
A session-scoped fixture could not use a module-scoped one in a
meaningful way.
pytest minimizes the number of active fixtures during test runs. If you have a parametrized fixture, then all the tests using it will first execute with one instance and then finalizers are called before the next fixture instance is created. Among other things, this eases testing of applications which create and use global state.
The following example uses two parametrized funcargs, one of which is
scoped on a per-module basis, and all the functions perform print calls
to show the setup/teardown flow:
# content of test_module.py
import pytest
@pytest.fixture(scope="module", params=["mod1", "mod2"])
def modarg(request):
param = request.param
print (" SETUP modarg %s" % param)
def fin():
print (" TEARDOWN modarg %s" % param)
request.addfinalizer(fin)
return param
@pytest.fixture(scope="function", params=[1,2])
def otherarg(request):
param = request.param
print (" SETUP otherarg %s" % param)
def fin():
print (" TEARDOWN otherarg %s" % param)
request.addfinalizer(fin)
return param
def test_0(otherarg):
print (" RUN test0 with otherarg %s" % otherarg)
def test_1(modarg):
print (" RUN test1 with modarg %s" % modarg)
def test_2(otherarg, modarg):
print (" RUN test2 with otherarg %s and modarg %s" % (otherarg, modarg))
Let's run the tests in verbose mode and with looking at the print-output:
$ py.test -v -s test_module.py ======= test session starts ======== platform linux -- Python 3.5.1, pytest-2.9.2, py-1.4.31, pluggy-0.3.1 -- $PYTHON_PREFIX/bin/python3.5 cachedir: .cache rootdir: $REGENDOC_TMPDIR, inifile: collecting ... collected 8 items test_module.py::test_0[1] SETUP otherarg 1 RUN test0 with otherarg 1 PASSED TEARDOWN otherarg 1 test_module.py::test_0[2] SETUP otherarg 2 RUN test0 with otherarg 2 PASSED TEARDOWN otherarg 2 test_module.py::test_1[mod1] SETUP modarg mod1 RUN test1 with modarg mod1 PASSED test_module.py::test_2[1-mod1] SETUP otherarg 1 RUN test2 with otherarg 1 and modarg mod1 PASSED TEARDOWN otherarg 1 test_module.py::test_2[2-mod1] SETUP otherarg 2 RUN test2 with otherarg 2 and modarg mod1 PASSED TEARDOWN otherarg 2 test_module.py::test_1[mod2] TEARDOWN modarg mod1 SETUP modarg mod2 RUN test1 with modarg mod2 PASSED test_module.py::test_2[1-mod2] SETUP otherarg 1 RUN test2 with otherarg 1 and modarg mod2 PASSED TEARDOWN otherarg 1 test_module.py::test_2[2-mod2] SETUP otherarg 2 RUN test2 with otherarg 2 and modarg mod2 PASSED TEARDOWN otherarg 2 TEARDOWN modarg mod2 ======= 8 passed in 0.12 seconds ========
You can see that the parametrized module-scoped modarg resource caused an
ordering of test execution that lead to the fewest possible "active" resources.
The finalizer for the mod1 parametrized resource was executed before the
mod2 resource was setup.
In particular notice that test_0 is completely independent and finishes first.
Then test_1 is executed with mod1, then test_2 with mod1, then test_1
with mod2 and finally test_2 with mod2.
The otherarg parametrized resource (having function scope) was set up before
and teared down after every test that used it.
Sometimes test functions do not directly need access to a fixture object. For example, tests may require to operate with an empty directory as the current working directory but otherwise do not care for the concrete directory. Here is how you can can use the standard tempfile and pytest fixtures to achieve it. We separate the creation of the fixture into a conftest.py file:
# content of conftest.py
import pytest
import tempfile
import os
@pytest.fixture()
def cleandir():
newpath = tempfile.mkdtemp()
os.chdir(newpath)
and declare its use in a test module via a usefixtures marker:
# content of test_setenv.py
import os
import pytest
@pytest.mark.usefixtures("cleandir")
class TestDirectoryInit:
def test_cwd_starts_empty(self):
assert os.listdir(os.getcwd()) == []
with open("myfile", "w") as f:
f.write("hello")
def test_cwd_again_starts_empty(self):
assert os.listdir(os.getcwd()) == []
Due to the usefixtures marker, the cleandir fixture
will be required for the execution of each test method, just as if
you specified a "cleandir" function argument to each of them. Let's run it
to verify our fixture is activated and the tests pass:
$ py.test -q .. 2 passed in 0.12 seconds
You can specify multiple fixtures like this:
@pytest.mark.usefixtures("cleandir", "anotherfixture")and you may specify fixture usage at the test module level, using a generic feature of the mark mechanism:
pytestmark = pytest.mark.usefixtures("cleandir")Note that the assigned variable must be called pytestmark, assigning e.g.
foomark will not activate the fixtures.
Lastly you can put fixtures required by all tests in your project into an ini-file:
# content of pytest.ini
[pytest]
usefixtures = cleandirOccasionally, you may want to have fixtures get invoked automatically without a usefixtures or funcargs reference. As a practical example, suppose we have a database fixture which has a begin/rollback/commit architecture and we want to automatically surround each test method by a transaction and a rollback. Here is a dummy self-contained implementation of this idea:
# content of test_db_transact.py
import pytest
class DB:
def __init__(self):
self.intransaction = []
def begin(self, name):
self.intransaction.append(name)
def rollback(self):
self.intransaction.pop()
@pytest.fixture(scope="module")
def db():
return DB()
class TestClass:
@pytest.fixture(autouse=True)
def transact(self, request, db):
db.begin(request.function.__name__)
request.addfinalizer(db.rollback)
def test_method1(self, db):
assert db.intransaction == ["test_method1"]
def test_method2(self, db):
assert db.intransaction == ["test_method2"]
The class-level transact fixture is marked with autouse=true
which implies that all test methods in the class will use this fixture
without a need to state it in the test function signature or with a
class-level usefixtures decorator.
If we run it, we get two passing tests:
$ py.test -q .. 2 passed in 0.12 seconds
Here is how autouse fixtures work in other scopes:
- if an autouse fixture is defined in a test module, all its test functions automatically use it.
- if an autouse fixture is defined in a conftest.py file then all tests in all test modules below its directory will invoke the fixture.
- lastly, and please use that with care: if you define an autouse fixture in a plugin, it will be invoked for all tests in all projects where the plugin is installed. This can be useful if a fixture only anyway works in the presence of certain settings e. g. in the ini-file. Such a global fixture should always quickly determine if it should do any work and avoid otherwise expensive imports or computation.
Note that the above transact fixture may very well be a fixture that
you want to make available in your project without having it generally
active. The canonical way to do that is to put the transact definition
into a conftest.py file without using autouse:
# content of conftest.py
@pytest.fixture()
def transact(self, request, db):
db.begin()
request.addfinalizer(db.rollback)
and then e.g. have a TestClass using it by declaring the need:
@pytest.mark.usefixtures("transact")
class TestClass:
def test_method1(self):
...
All test methods in this TestClass will use the transaction fixture while
other test classes or functions in the module will not use it unless
they also add a transact reference.
If during implementing your tests you realize that you
want to use a fixture function from multiple test files you can move it
to a :ref:`conftest.py <conftest.py>` file or even separately installable
:ref:`plugins <plugins>` without changing test code. The discovery of
fixtures functions starts at test classes, then test modules, then
conftest.py files and finally builtin and third party plugins.
In relatively large test suite, you most likely need to override a global or root fixture with a locally
defined one, keeping the test code readable and maintainable.
Given the tests file structure is:
tests/
__init__.py
conftest.py
# content of tests/conftest.py
import pytest
@pytest.fixture
def username():
return 'username'
test_something.py
# content of tests/test_something.py
def test_username(username):
assert username == 'username'
subfolder/
__init__.py
conftest.py
# content of tests/subfolder/conftest.py
import pytest
@pytest.fixture
def username(username):
return 'overridden-' + username
test_something.py
# content of tests/subfolder/test_something.py
def test_username(username):
assert username == 'overridden-username'
As you can see, a fixture with the same name can be overridden for certain test folder level.
Note that the base or super fixture can be accessed from the overriding
fixture easily - used in the example above.
Given the tests file structure is:
tests/
__init__.py
conftest.py
# content of tests/conftest.py
@pytest.fixture
def username():
return 'username'
test_something.py
# content of tests/test_something.py
import pytest
@pytest.fixture
def username(username):
return 'overridden-' + username
def test_username(username):
assert username == 'overridden-username'
test_something_else.py
# content of tests/test_something_else.py
import pytest
@pytest.fixture
def username(username):
return 'overridden-else-' + username
def test_username(username):
assert username == 'overridden-else-username'
In the example above, a fixture with the same name can be overridden for certain test module.
Given the tests file structure is:
tests/
__init__.py
conftest.py
# content of tests/conftest.py
import pytest
@pytest.fixture
def username():
return 'username'
@pytest.fixture
def other_username(username):
return 'other-' + username
test_something.py
# content of tests/test_something.py
import pytest
@pytest.mark.parametrize('username', ['directly-overridden-username'])
def test_username(username):
assert username == 'directly-overridden-username'
@pytest.mark.parametrize('username', ['directly-overridden-username-other'])
def test_username_other(other_username):
assert username == 'other-directly-overridden-username-other'
In the example above, a fixture value is overridden by the test parameter value. Note that the value of the fixture can be overridden this way even if the test doesn't use it directly (doesn't mention it in the function prototype).
Given the tests file structure is:
tests/
__init__.py
conftest.py
# content of tests/conftest.py
import pytest
@pytest.fixture(params=['one', 'two', 'three'])
def parametrized_username(request):
return request.param
@pytest.fixture
def non_parametrized_username(request):
return 'username'
test_something.py
# content of tests/test_something.py
import pytest
@pytest.fixture
def parametrized_username():
return 'overridden-username'
@pytest.fixture(params=['one', 'two', 'three'])
def non_parametrized_username(request):
return request.param
def test_username(parametrized_username):
assert parametrized_username == 'overridden-username'
def test_parametrized_username(non_parametrized_username):
assert non_parametrized_username in ['one', 'two', 'three']
test_something_else.py
# content of tests/test_something_else.py
def test_username(parametrized_username):
assert parametrized_username in ['one', 'two', 'three']
def test_username(non_parametrized_username):
assert non_parametrized_username == 'username'
In the example above, a parametrized fixture is overridden with a non-parametrized version, and a non-parametrized fixture is overridden with a parametrized version for certain test module. The same applies for the test folder level obviously.