In Python 3.10, I have a function like:
from shutil import which
def my_func():
if which('myexecutable.sh'):
# do stuff
else:
# do other stuff
I would like to write a unit test with Pytest that runs the first part code even though the executable is not present. What is the best way to do this?
I know that I can use monkeypatch.setenv() to set an environment variable, but that's not going to make the which() check pass. There's also the added challenge of making sure this is compatible on Windows and Linux.
You could try like this:
# in script file
from shutil import which
def myfunc():
if which("myexecutable.sh"):
return "OK"
else:
...
# in test file
import pytest
from script import myfunc
#pytest.fixture
def which(mocker):
return mocker.patch("script.which", autospec=True)
def test_myfunc(which):
assert myfunc() == "OK"
Running pytest outputs: 1 passed
I want to run doc-tests of a Python script as part of a pre-commit hook in Python.
In the file set_prefix.py, I have doc-tests in front of functions, which I test before running with:
import doctest
import sys
EXTENSIONS = tuple([".%s" % ending for ending in ["jpg", "heic", "nrw"]])
def is_target_for_renaming(filepath):
"""Returns true if this filepath should be renamed.
>>> is_target_for_renaming("/Users/username/Pictures/document.other_jpg")
True
"""
return filepath.lower().endswith(EXTENSIONS)
def get_failed_tests():
r = doctest.testmod()
return r.failed
def main():
pass
if "__main__" == __name__:
args = sys.argv
test_only = 2 <= len(sys.argv) and "test" == sys.argv[1]
test_failures = get_failed_tests()
print(test_failures)
assert 0 == test_failures
if not test_only:
main()
When I run python3 set_prefix.py test, I get the error I expected.
Yet, when I import the module and call the function:
import set_prefix
if "__main__" == __name__:
test_failures = set_prefix.get_failed_tests()
print(test_failures)
I get 0 failures:
$ python3 temp.py
0
The reason I want to import the module is to run the tests in a pre-commit hook similar to that added by flake8:
#!/usr/local/opt/python/bin/python3.7
import sys
from flake8.main import git
if __name__ == '__main__':
sys.exit(
git.hook(
strict=git.config_for('strict'),
lazy=git.config_for('lazy'),
)
)
Why do the doc-tests run when called from the command-line and the script and not when the script is imported? Would unittest be a better framework, as described in this thread?
doctest.testmod()
runs doctests in __main__ module and it depends on which script you're actually running.
You can fix this with m parameter, but you'll still be forced to add boilerplate code in each module that has doctests. Try this:
doctest.testfile("some_module.py")
How can I get test_greet to run in the below; note: test_one(when uncommented) is seen and run by the test runner; to be specific, I want the line unittest.main() to correctly pick up the module level test (test_greet).
import unittest
#class MyTests(unittest.TestCase):
# def test_one(self):
# assert 1==2
def test_greet():
assert 1==3
if __name__=="__main__":
unittest.main()
Let's say i have a file called MyTests.py as below:
import unittest
class MyTests(unittest.TestCase):
def test_greet(self):
self.assertEqual(1,3)
Then:
Open a CMD in the folder that MyTests.py exists
Run python -m unittest MyTests
Please note that, all your tests must have the test_ otherwise, it will not be run.
Say I have a module with the following:
def main():
pass
if __name__ == "__main__":
main()
I want to write a unit test for the bottom half (I'd like to achieve 100% coverage). I discovered the runpy builtin module that performs the import/__name__-setting mechanism, but I can't figure out how to mock or otherwise check that the main() function is called.
This is what I've tried so far:
import runpy
import mock
#mock.patch('foobar.main')
def test_main(self, main):
runpy.run_module('foobar', run_name='__main__')
main.assert_called_once_with()
I will choose another alternative which is to exclude the if __name__ == '__main__' from the coverage report , of course you can do that only if you already have a test case for your main() function in your tests.
As for why I choose to exclude rather than writing a new test case for the whole script is because if as I stated you already have a test case for your main() function the fact that you add an other test case for the script (just for having a 100 % coverage) will be just a duplicated one.
For how to exclude the if __name__ == '__main__' you can write a coverage configuration file and add in the section report:
[report]
exclude_lines =
if __name__ == .__main__.:
More info about the coverage configuration file can be found here.
Hope this can help.
You can do this using the imp module rather than the import statement. The problem with the import statement is that the test for '__main__' runs as part of the import statement before you get a chance to assign to runpy.__name__.
For example, you could use imp.load_source() like so:
import imp
runpy = imp.load_source('__main__', '/path/to/runpy.py')
The first parameter is assigned to __name__ of the imported module.
Whoa, I'm a little late to the party, but I recently ran into this issue and I think I came up with a better solution, so here it is...
I was working on a module that contained a dozen or so scripts all ending with this exact copypasta:
if __name__ == '__main__':
if '--help' in sys.argv or '-h' in sys.argv:
print(__doc__)
else:
sys.exit(main())
Not horrible, sure, but not testable either. My solution was to write a new function in one of my modules:
def run_script(name, doc, main):
"""Act like a script if we were invoked like a script."""
if name == '__main__':
if '--help' in sys.argv or '-h' in sys.argv:
sys.stdout.write(doc)
else:
sys.exit(main())
and then place this gem at the end of each script file:
run_script(__name__, __doc__, main)
Technically, this function will be run unconditionally whether your script was imported as a module or ran as a script. This is ok however because the function doesn't actually do anything unless the script is being ran as a script. So code coverage sees the function runs and says "yes, 100% code coverage!" Meanwhile, I wrote three tests to cover the function itself:
#patch('mymodule.utils.sys')
def test_run_script_as_import(self, sysMock):
"""The run_script() func is a NOP when name != __main__."""
mainMock = Mock()
sysMock.argv = []
run_script('some_module', 'docdocdoc', mainMock)
self.assertEqual(mainMock.mock_calls, [])
self.assertEqual(sysMock.exit.mock_calls, [])
self.assertEqual(sysMock.stdout.write.mock_calls, [])
#patch('mymodule.utils.sys')
def test_run_script_as_script(self, sysMock):
"""Invoke main() when run as a script."""
mainMock = Mock()
sysMock.argv = []
run_script('__main__', 'docdocdoc', mainMock)
mainMock.assert_called_once_with()
sysMock.exit.assert_called_once_with(mainMock())
self.assertEqual(sysMock.stdout.write.mock_calls, [])
#patch('mymodule.utils.sys')
def test_run_script_with_help(self, sysMock):
"""Print help when the user asks for help."""
mainMock = Mock()
for h in ('-h', '--help'):
sysMock.argv = [h]
run_script('__main__', h*5, mainMock)
self.assertEqual(mainMock.mock_calls, [])
self.assertEqual(sysMock.exit.mock_calls, [])
sysMock.stdout.write.assert_called_with(h*5)
Blam! Now you can write a testable main(), invoke it as a script, have 100% test coverage, and not need to ignore any code in your coverage report.
Python 3 solution:
import os
from importlib.machinery import SourceFileLoader
from importlib.util import spec_from_loader, module_from_spec
from importlib import reload
from unittest import TestCase
from unittest.mock import MagicMock, patch
class TestIfNameEqMain(TestCase):
def test_name_eq_main(self):
loader = SourceFileLoader('__main__',
os.path.join(os.path.dirname(os.path.dirname(__file__)),
'__main__.py'))
with self.assertRaises(SystemExit) as e:
loader.exec_module(module_from_spec(spec_from_loader(loader.name, loader)))
Using the alternative solution of defining your own little function:
# module.py
def main():
if __name__ == '__main__':
return 'sweet'
return 'child of mine'
You can test with:
# Override the `__name__` value in your module to '__main__'
with patch('module_name.__name__', '__main__'):
import module_name
self.assertEqual(module_name.main(), 'sweet')
with patch('module_name.__name__', 'anything else'):
reload(module_name)
del module_name
import module_name
self.assertEqual(module_name.main(), 'child of mine')
I did not want to exclude the lines in question, so based on this explanation of a solution, I implemented a simplified version of the alternate answer given here...
I wrapped if __name__ == "__main__": in a function to make it easily testable, and then called that function to retain logic:
# myapp.module.py
def main():
pass
def init():
if __name__ == "__main__":
main()
init()
I mocked the __name__ using unittest.mock to get at the lines in question:
from unittest.mock import patch, MagicMock
from myapp import module
def test_name_equals_main():
# Arrange
with patch.object(module, "main", MagicMock()) as mock_main:
with patch.object(module, "__name__", "__main__"):
# Act
module.init()
# Assert
mock_main.assert_called_once()
If you are sending arguments into the mocked function, like so,
if __name__ == "__main__":
main(main_args)
then you can use assert_called_once_with() for an even better test:
expected_args = ["expected_arg_1", "expected_arg_2"]
mock_main.assert_called_once_with(expected_args)
If desired, you can also add a return_value to the MagicMock() like so:
with patch.object(module, "main", MagicMock(return_value='foo')) as mock_main:
One approach is to run the modules as scripts (e.g. os.system(...)) and compare their stdout and stderr output to expected values.
I found this solution helpful. Works well if you use a function to keep all your script code.
The code will be handled as one code line. It doesn't matter if the entire line was executed for coverage counter (though this is not what you would actually actually expect by 100% coverage)
The trick is also accepted pylint. ;-)
if __name__ == '__main__': \
main()
If it's just to get the 100% and there is nothing "real" to test there, it is easier to ignore that line.
If you are using the regular coverage lib, you can just add a simple comment, and the line will be ignored in the coverage report.
if __name__ == '__main__':
main() # pragma: no cover
https://coverage.readthedocs.io/en/coverage-4.3.3/excluding.html
Another comment by # Taylor Edmiston also mentions it
My solution is to use imp.load_source() and force an exception to be raised early in main() by not providing a required CLI argument, providing a malformed argument, setting paths in such a way that a required file is not found, etc.
import imp
import os
import sys
def mainCond(testObj, srcFilePath, expectedExcType=SystemExit, cliArgsStr=''):
sys.argv = [os.path.basename(srcFilePath)] + (
[] if len(cliArgsStr) == 0 else cliArgsStr.split(' '))
testObj.assertRaises(expectedExcType, imp.load_source, '__main__', srcFilePath)
Then in your test class you can use this function like this:
def testMain(self):
mainCond(self, 'path/to/main.py', cliArgsStr='-d FailingArg')
To import your "main" code in pytest in order to test it you can import main module like other functions thanks to native importlib package :
def test_main():
import importlib
loader = importlib.machinery.SourceFileLoader("__main__", "src/glue_jobs/move_data_with_resource_partitionning.py")
runpy_main = loader.load_module()
assert runpy_main()
I use testoob in the following way:
def suite():
import unittest
return unittest.TestLoader().loadTestsFromNames([
'my_module.my_unittest_class',
'my_module.my_other_unittest_class',
])
if __name__ == '__main__':
import testoob
testoob.main(defaultTest="suite")
And then run the unittest suite with the following:
python my_unittest.py --coverage=normal
This however will also print code coverage figures of all modules that my module and unittest depends on, which I'm not interested in at all. How can I configure testoob to only report coverage for my own module?
I ended up overriding the private _should_cover_frame function in the testoob Coverage class and comparing the frame's file path to my module. Not the nicest solution, but at least it works.
from testoob.coverage import Coverage
orig_should_cover = Coverage._should_cover_frame
def my_should_cover_frame(self, frame):
from os.path import abspath
filename = abspath(frame.f_code.co_filename)
if filename.find('my_module') == -1:
return False
else:
return orig_should_cover(self, frame)
Coverage._should_cover_frame = my_should_cover_frame