Create and import helper functions in tests without creating packages in test directory using py.test
Question:
Question
How can I import helper functions in test files without creating packages in the test directory?
Context
I’d like to create a test helper function that I can import in several tests. Say, something like this:
# In common_file.py
def assert_a_general_property_between(x, y):
# test a specific relationship between x and y
assert ...
# In test/my_test.py
def test_something_with(x):
some_value = some_function_of_(x)
assert_a_general_property_between(x, some_value)
Using Python 3.5, with py.test 2.8.2
Current “solution”
I’m currently doing this via importing a module inside my project’s test directory (which is now a package), but I’d like to do it with some other mechanism if possible (so that my test directory doesn’t have packages but just tests, and the tests can be run on an installed version of the package, as is recommended here in the py.test documentation on good practices).
Answers:
my option is to create an extra dir in tests dir and add it to pythonpath in the conftest so.
tests/
helpers/
utils.py
...
conftest.py
setup.cfg
in the conftest.py
import sys
import os
sys.path.append(os.path.join(os.path.dirname(__file__), 'helpers'))
in setup.cfg
[pytest]
norecursedirs=tests/helpers
this module will be available with import utils, only be careful to name clashing.
While searching for a solution for this problem I came across this SO question and ended up adopting the same approach. Creating a helpers package, munging sys.path to make it importable and then just importing it…
This did not seem the best approach, so, I created pytest-helpers-namespace. This plugin allows you to register helper functions on your conftest.py:
import pytest
pytest_plugins = ['helpers_namespace']
@pytest.helpers.register
def my_custom_assert_helper(blah):
assert blah
# One can even specify a custom name for the helper
@pytest.helpers.register(name='assertme')
def my_custom_assert_helper_2(blah):
assert blah
# And even namespace helpers
@pytest.helpers.asserts.register(name='me')
def my_custom_assert_helper_3(blah):
assert blah
And then, within a test case function body just use it like
def test_this():
assert pytest.helpers.my_custom_assert_helper(blah)
def test_this_2():
assert pytest.helpers.assertme(blah)
def test_this_3():
assert pytest.helpers.asserts.me(blah)
Its pretty simple and the documentation pretty small. Take a look and tell me if it addresses your problem too.
As another option, this directory structure worked for me:
mypkg/
...
test_helpers/
__init__.py
utils.py
...
tests/
my_test.py
...
And then in my_test.py import the utilities using:
from test_helpers import utils
You could define a helper class in conftest.py, then create a fixture that returns that class (or an instance of it, depending on what you need).
import pytest
class Helpers:
@staticmethod
def help_me():
return "no"
@pytest.fixture
def helpers():
return Helpers
Then in your tests, you can use the fixture:
def test_with_help(helpers):
helpers.help_me()
Create a helpers package in tests folder:
tests/
helpers/
__init__.py
utils.py
...
# make sure no __init__.py in here!
setup.cfg
in setup.cfg:
[pytest]
norecursedirs=tests/helpers
the helpers will be available with import helpers.
To access a method from different modules without creating packages, and have that function operate as a helper function I found the following helpful:
conftest.py:
@pytest.fixture
def compare_test_vs_actual():
def a_function(test, actual):
print(test, actual)
return a_function
test_file.py:
def test_service_command_add(compare_test_vs_actual):
compare_test_vs_actual("hello", "world")
It is possible that some of you will be completely uphold by my suggestion. However, very simple way of using common function or value from other modules is to inject it directly into a common workspace. Example:
conftest.py:
import sys
def my_function():
return 'my_function() called'
sys.modules['pytest'].common_funct = my_function
test_me.py
import pytest
def test_A():
print(pytest.common_funct())
With pytest 7 (at least) the easiest way to accomplish this is to add the following configuration to you pytest.ini or pyproject.toml. This adds the tests directory to your sys.path and makes the respective modules available:
pythonpath = ["tests"]
Maybe it’s even better to separate test-helpers from the tests, but that’s a matter of style.
As an example, using a separate directory, and using a pyproject.toml it would look like this:
[tool.pytest.ini_options]
pythonpath = ["test_helpers"]
testpaths = ["tests"]
addopts = [
"--import-mode=importlib",
]
src/
...
tests/
...
test_helpers/
...
This configures the importlib import mode recommended here, designed exactly to prevent modifying the sys.path, though, if you are careful with your naming and you need to extract common test helpers, this can be a viable option.
Question
How can I import helper functions in test files without creating packages in the test directory?
Context
I’d like to create a test helper function that I can import in several tests. Say, something like this:
# In common_file.py
def assert_a_general_property_between(x, y):
# test a specific relationship between x and y
assert ...
# In test/my_test.py
def test_something_with(x):
some_value = some_function_of_(x)
assert_a_general_property_between(x, some_value)
Using Python 3.5, with py.test 2.8.2
Current “solution”
I’m currently doing this via importing a module inside my project’s test directory (which is now a package), but I’d like to do it with some other mechanism if possible (so that my test directory doesn’t have packages but just tests, and the tests can be run on an installed version of the package, as is recommended here in the py.test documentation on good practices).
my option is to create an extra dir in tests dir and add it to pythonpath in the conftest so.
tests/
helpers/
utils.py
...
conftest.py
setup.cfg
in the conftest.py
import sys
import os
sys.path.append(os.path.join(os.path.dirname(__file__), 'helpers'))
in setup.cfg
[pytest]
norecursedirs=tests/helpers
this module will be available with import utils, only be careful to name clashing.
While searching for a solution for this problem I came across this SO question and ended up adopting the same approach. Creating a helpers package, munging sys.path to make it importable and then just importing it…
This did not seem the best approach, so, I created pytest-helpers-namespace. This plugin allows you to register helper functions on your conftest.py:
import pytest
pytest_plugins = ['helpers_namespace']
@pytest.helpers.register
def my_custom_assert_helper(blah):
assert blah
# One can even specify a custom name for the helper
@pytest.helpers.register(name='assertme')
def my_custom_assert_helper_2(blah):
assert blah
# And even namespace helpers
@pytest.helpers.asserts.register(name='me')
def my_custom_assert_helper_3(blah):
assert blah
And then, within a test case function body just use it like
def test_this():
assert pytest.helpers.my_custom_assert_helper(blah)
def test_this_2():
assert pytest.helpers.assertme(blah)
def test_this_3():
assert pytest.helpers.asserts.me(blah)
Its pretty simple and the documentation pretty small. Take a look and tell me if it addresses your problem too.
As another option, this directory structure worked for me:
mypkg/
...
test_helpers/
__init__.py
utils.py
...
tests/
my_test.py
...
And then in my_test.py import the utilities using:
from test_helpers import utils
You could define a helper class in conftest.py, then create a fixture that returns that class (or an instance of it, depending on what you need).
import pytest
class Helpers:
@staticmethod
def help_me():
return "no"
@pytest.fixture
def helpers():
return Helpers
Then in your tests, you can use the fixture:
def test_with_help(helpers):
helpers.help_me()
Create a helpers package in tests folder:
tests/
helpers/
__init__.py
utils.py
...
# make sure no __init__.py in here!
setup.cfg
in setup.cfg:
[pytest]
norecursedirs=tests/helpers
the helpers will be available with import helpers.
To access a method from different modules without creating packages, and have that function operate as a helper function I found the following helpful:
conftest.py:
@pytest.fixture
def compare_test_vs_actual():
def a_function(test, actual):
print(test, actual)
return a_function
test_file.py:
def test_service_command_add(compare_test_vs_actual):
compare_test_vs_actual("hello", "world")
It is possible that some of you will be completely uphold by my suggestion. However, very simple way of using common function or value from other modules is to inject it directly into a common workspace. Example:
conftest.py:
import sys
def my_function():
return 'my_function() called'
sys.modules['pytest'].common_funct = my_function
test_me.py
import pytest
def test_A():
print(pytest.common_funct())
With pytest 7 (at least) the easiest way to accomplish this is to add the following configuration to you pytest.ini or pyproject.toml. This adds the tests directory to your sys.path and makes the respective modules available:
pythonpath = ["tests"]
Maybe it’s even better to separate test-helpers from the tests, but that’s a matter of style.
As an example, using a separate directory, and using a pyproject.toml it would look like this:
[tool.pytest.ini_options]
pythonpath = ["test_helpers"]
testpaths = ["tests"]
addopts = [
"--import-mode=importlib",
]
src/
...
tests/
...
test_helpers/
...
This configures the importlib import mode recommended here, designed exactly to prevent modifying the sys.path, though, if you are careful with your naming and you need to extract common test helpers, this can be a viable option.