I am using pytest and would like to invoke a test function for a number of objects returned by a server, and for a number of servers.
The servers are defined in a YAML file and those definitions are provided as parametrization to a fixture "server_connection" that returns a Connection object for a single server. Due to the parametrization, it causes the test function to be invoked once for each server.
I am able to do this with a loop in the test function: There is a second fixture "server_objects" that takes a "server_connection" fixture as input and returns a list of server objects. The pytest test function then takes that second fixture and executes the actual test in a loop through the server objects.
Here is that code:
import pytest
SD_LIST = ... # read list of server definitions from YAML file
#pytest.fixture(
params=SD_LIST,
scope='module'
)
def server_connection(request):
server_definition = request.param
return Connection(server_definition.url, ...)
#pytest.fixture(
scope='module'
)
def server_objects(request, server_connection):
return server_connection.get_objects()
def test_object_foo(server_objects):
for server_object in server_objects:
# Perform test for a single server object:
assert server_object == 'foo'
However, the disadvantage is of course that a test failure causes the entire test function to end.
What I want to happen instead is that the test function is invoked for each single server object, so that a test failure for one object does not prevent the tests on the other objects. Ideally, I'd like to have a fixture that provides a single server object, that I can pass to the test function:
...
#pytest.fixture(
scope='module'
)
def server_object(request, server_connection):
server_objects = server_connection.get_objects()
# TBD: Some magic to parametrize this fixture with server_objects
def test_object_foo(server_object):
# Perform test for a single server object:
assert server_object == 'foo'
I have read through all pytest docs regarding fixtures but did not find a way to do this.
I know about pytest hooks and have used e.g. pytest_generate_tests() before, but I did not find a way how pytest_generate_tests() can access the values of other fixtures.
Any ideas?
Update: Let me add that I also did search SO for this, but did not find an answer. I specifically looked at:
pytest fixture of fixtures
How to parametrize a Pytest fixture
py.test: Pass a parameter to a fixture function
initing a pytest fixture with a parameter
Related
Is there possibility to parametrize fixture from a fixture?
Let's say I've a fixture, which is taking relay_number as a parameter:
#pytest.fixture
def unipi_relay(request):
try:
relay_number = request.param["relay_number"]
except KeyError:
raise ValueError(
"This function requires as a parameter dictionary with values for keys:"
"\nrelay_number - passed as integer\n"
)
relay = RelayFactory.get_unipi_relay(relay_number)
relay.reset()
yield relay
relay.reset()
Now I would like to have another fixture, which will yield unipi_relay with already passed parameter.
Reason why I want to implement such a solution is that I would like to reuse unipi_relay fixture a few times in single test.
I'm not sure if I'm understanding correctly what you want to achieve because you haven't put the parameters your fixture is taking. Maybe the “factory as fixture” pattern is what you're looking for, because you'll then be able to reuse the unipi_relay fixture. Please also have a look at the question Reusing pytest fixture in the same test.
I'm a starter with pytest. Just learned about fixture and tried to do this:
My tests call functions I wrote, and get test data from a code practicing website.
Each test is from a particular page and has several sets of test data.
So, I want to use #pytest.mark.parametrize to parametrize my single test func.
Also, as the operations of the tests are samelike, I want to made the pageObject instantiation and the steps to get test data from page as a fixture.
# content of conftest.py
#pytest.fixture
def get_testdata_from_problem_page():
def _get_testdata_from_problem_page(problem_name):
page = problem_page.ProblemPage(problem_name)
return page.get_sample_data()
return _get_testdata_from_problem_page
# content of test_problem_a.py
import pytest
from page_objects import problem_page
from problem_func import problem_a
#pytest.mark.parametrize('input,expected', test_data)
def test_problem_a(get_testdata_from_problem_page):
input, expected = get_testdata_from_problem_page("problem_a")
assert problem_a.problem_a(input) == expected
Then I realized, as above, I can't parametrize the test using pytest.mark as the test_data should be given outside the test function....
Are there solutions for this? Thanks very much~~
If I understand you correctly, you want to write one parameterized test per page. In this case you just have to write a function instead of a fixture and use that for parametrization:
import pytest
from page_objects import problem_page
from problem_func import problem_a
def get_testdata_from_problem_page(problem_name):
page = problem_page.ProblemPage(problem_name)
# returns a list of (input, expected) tuples
return page.get_sample_data()
#pytest.mark.parametrize('input,expected',
get_testdata_from_problem_page("problem_a"))
def test_problem_a(input, expected):
assert problem_a.problem_a(input) == expected
As you wrote, a fixture can only be used as a parameter to a test function or to another fixture, not in a decorator.
If you want to use the function to get test data elsewhere, just move it to a common module and import it. This can be just some custom utility module, or you could put it into contest.py, though you still have to import it.
Note also that the fixture you wrote does not do anything - it defines a local function that is not called and returns.
I have a parameterized pytest test method, test_1. Before all the parameterized cases are run for this test method, I'd like to call another method, tmp_db_uri, which creates a temporary database and yields the uri for the database. I only want to call that generator once, so that I can use the same temporary database for all the test cases. I thought that if I called it from a fixture (db_uri), that would do the trick, since I thought that fixtures are created once per test, but it seems that the fixture is getting called for each case in this test, and a new temporary database is being created each time.
What is the correct way to do this? Is there a way to run a setup for this method before all the cases are run, to use just one tmp_db_uri? I don't want the temporary database hanging around for the entire test module - just for the duration of this one test (cleanup is handled by a context manager on tmp_db_uri).
I currently have something that looks similar to this:
#pytest.fixture
def db_uri(tmp_db_uri):
return tmp_db_uri
#pytest.mark.parameterize(("item1","item2"), ((1, "a"), (2, "b")))
def test_1(item1, item2, db_uri):
print("do something")
You can create a module level fixture ,so that it's created only once for the entire test module or you can create a global variable and return the db if it is already created or create otherwise.
#pytest.fixture(scope="module")
def db_uri(tmp_db_uri):
return tmp_db_uri
or
TMP_DB = None
#pytest.fixture
def db_uri(tmp_db_uri):
global TMP_DB
if not TMP_DB:
# do your stuff to create tmp_db
TMP_DB = tmp_db_uri
return TMP_DB
I am building some tests for python3 code using py.test. The code accesses a Postgresql Database using aiopg (Asyncio based interface to postgres).
My main expectations:
Every test case should have access to a new asyncio event loop.
A test that runs too long will stop with a timeout exception.
Every test case should have access to a database connection.
I don't want to repeat myself when writing the test cases.
Using py.test fixtures I can get pretty close to what I want, but I still have to repeat myself a bit in every asynchronous test case.
This is how my code looks like:
#pytest.fixture(scope='function')
def tloop(request):
# This fixture is responsible for getting a new event loop
# for every test, and close it when the test ends.
...
def run_timeout(cor,loop,timeout=ASYNC_TEST_TIMEOUT):
"""
Run a given coroutine with timeout.
"""
task_with_timeout = asyncio.wait_for(cor,timeout)
try:
loop.run_until_complete(task_with_timeout)
except futures.TimeoutError:
# Timeout:
raise ExceptAsyncTestTimeout()
#pytest.fixture(scope='module')
def clean_test_db(request):
# Empty the test database.
...
#pytest.fixture(scope='function')
def udb(request,clean_test_db,tloop):
# Obtain a connection to the database using aiopg
# (That's why we need tloop here).
...
# An example for a test:
def test_insert_user(tloop,udb):
#asyncio.coroutine
def insert_user():
# Do user insertion here ...
yield from udb.insert_new_user(...
...
run_timeout(insert_user(),tloop)
I can live with the solution that I have so far, but it can get cumbersome to define an inner coroutine and add the run_timeout line for every asynchronous test that I write.
I want my tests to look somewhat like this:
#some_magic_decorator
def test_insert_user(udb):
# Do user insertion here ...
yield from udb.insert_new_user(...
...
I attempted to create such a decorator in some elegant way, but failed. More generally, if my test looks like:
#some_magic_decorator
def my_test(arg1,arg2,...,arg_n):
...
Then the produced function (After the decorator is applied) should be:
def my_test_wrapper(tloop,arg1,arg2,...,arg_n):
run_timeout(my_test(),tloop)
Note that some of my tests use other fixtures (besides udb for example), and those fixtures must show up as arguments to the produced function, or else py.test will not invoke them.
I tried using both wrapt and decorator python modules to create such a magic decorator, however it seems like both of those modules help me create a function with a signature identical to my_test, which is not a good solution in this case.
This can probably solved using eval or a similar hack, but I was wondering if there is something elegant that I'm missing here.
I’m currently trying to solve a similar problem. Here’s what I’ve come up with so far. It seems to work but needs some clean-up:
# tests/test_foo.py
import asyncio
#asyncio.coroutine
def test_coro(loop):
yield from asyncio.sleep(0.1)
assert 0
# tests/conftest.py
import asyncio
#pytest.yield_fixture
def loop():
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
yield loop
loop.close()
def pytest_pycollect_makeitem(collector, name, obj):
"""Collect asyncio coroutines as normal functions, not as generators."""
if asyncio.iscoroutinefunction(obj):
return list(collector._genfunctions(name, obj))
def pytest_pyfunc_call(pyfuncitem):
"""If ``pyfuncitem.obj`` is an asyncio coroutinefunction, execute it via
the event loop instead of calling it directly."""
testfunction = pyfuncitem.obj
if not asyncio.iscoroutinefunction(testfunction):
return
# Copied from _pytest/python.py:pytest_pyfunc_call()
funcargs = pyfuncitem.funcargs
testargs = {}
for arg in pyfuncitem._fixtureinfo.argnames:
testargs[arg] = funcargs[arg]
coro = testfunction(**testargs) # Will no execute the test yet!
# Run the coro in the event loop
loop = testargs.get('loop', asyncio.get_event_loop())
loop.run_until_complete(coro)
return True # TODO: What to return here?
So I basically let pytest collect asyncio coroutines like normal functions. I also intercept text exectuion for functions. If the to-be-tested function is a coroutine, I execute it in the event loop. It works with or without a fixture creating a new event loop instance per test.
Edit: According to Ronny Pfannschmidt, something like this will be added to pytest after the 2.7 release. :-)
Every test case should have access to a new asyncio event loop.
The test suite of asyncio uses unittest.TestCase. It uses setUp() method to create a new event loop. addCleanup(loop.close) is close automatically the event loop, even on error.
Sorry, I don't know how to write this with py.test if you don't want to use TestCase. But if I remember correctly, py.test supports unittest.TestCase.
A test that runs too long will stop with a timeout exception.
You can use loop.call_later() with a function which raises a BaseException as a watch dog.
I am trying to use a pytest fixture (scope=module) in a class skipif decorator, but I am getting an error saying the fixture is not defined. Is this possible?
conftest.py has a fixture with module scope called 'target' that returns a CurrentTarget object.
The CurrentTarget object has a function isCommandSupported.
test_mytest.py has a class Test_MyTestClass that contains a dozen test functions.
I want to skip all the tests in Test_MyTestClass based on if the fixture target.isCommandSupported so I decorate Test_MyTestClass with skipif like:
#pytest.mark.skipif(not target.isCommandSupprted('commandA), reason=command not supported')
class Test_MyTestClass:
...
I get this error: NameError: name 'target' is not defined
If I try:
#pytest.mark.skipif(not pytest.config.getvalue('tgt').isCommandSupprted('commandA), reason=command not supported')
class Test_MyTestClass:
...
I get this error: AttributeError: 'function' object has no attribute 'isCommandSupprted'
The reason you get an error in the first case is that pytest injects fixtures, so they become available in your test functions via function parameters. They are never imported into higher scope.
The reason you get the AttributeError is that fixtures are functions and are evaluated at first (or each) use. So, when you get it through pytest.config it's still a function. This is the same reason the other answer will fail - if you import it, you're importing the fixture function, not it's result.
There is no direct way of doing what you want, but you can work around it with an extra fixture:
#pytest.fixture(scope='module')
def check_unsupported(target):
if not target.isCommandSupported('commandA'):
pytest.skip('command not supported')
#pytest.mark.usefixtures('check_unsupported')
def test_one():
pass
def test_two(check_unsupported):
pass
You can import target from conftest like so:
from conftest import target
Then, you can use it in pytest.mark.skipif as you were intending in your example.
#pytest.mark.skipif(not target.isCommandSupported('commandA'), reason='command not supported')
def Test_MyTestClass:
If you needed to repeat the same pytest.mark.skipif logic across several tests and wanted to avoid copy-pasting, a simple decorator will help:
check_unsupported = pytest.mark.skipif(not target.isCommandSupported('commandA'),
reason='command not supported')
#check_unsupported
def test_one():
pass
#check_unsupported
def test_two():
pass