Python unittest passing arguments

Question

In Python, how would I pass an argument from the command line to a unittest function?

Here is the code so far… I know it's wrong.

class TestingClass(unittest.TestCase):

    def testEmails(self):
        assertEqual(email_from_argument, "my_email@example.com")


if __name__ == "__main__":
    unittest.main(argv=[sys.argv[1]])
    email_from_argument = sys.argv[1]

Answer 1

So the doctors here that are saying "You say that hurts? Then don't do that!" are probably right. But if you really want to, here's one way of passing arguments to a unittest test:

import sys
import unittest

class MyTest(unittest.TestCase):
    USERNAME = "jemima"
    PASSWORD = "password"

    def test_logins_or_something(self):
        print('username:', self.USERNAME)
        print('password:', self.PASSWORD)


if __name__ == "__main__":
    if len(sys.argv) > 1:
        MyTest.USERNAME = sys.argv.pop()
        MyTest.PASSWORD = sys.argv.pop()
    unittest.main()

That will let you run with:

python mytests.py myusername mypassword

You need the argv.pop s, so your command line parameters don't mess with unittest's own...

The other thing you might want to look into is using environment variables:

import os
import unittest

class MyTest(unittest.TestCase):
    USERNAME = "jemima"
    PASSWORD = "password"

    def test_logins_or_something(self):
        print('username:', self.USERNAME)
        print('password:', self.PASSWORD)

if __name__ == "__main__":
    MyTest.USERNAME = os.environ.get('TEST_USERNAME', MyTest.USERNAME)
    MyTest.PASSWORD = os.environ.get('TEST_PASSWORD', MyTest.PASSWORD)
    unittest.main()

That will let you run with:

TEST_USERNAME=ausername TEST_PASSWORD=apassword python mytests.py

And it has the advantage that you're not messing with unittest's own argument parsing. The downside is it won't work quite like that on Windows...

Answer 2

Another method for those who really want to do this in spite of the correct remarks that you shouldn't:

import unittest

class MyTest(unittest.TestCase):

    def __init__(self, testName, extraArg):
        super(MyTest, self).__init__(testName)  # calling the super class init varies for different python versions.  This works for 2.7
        self.myExtraArg = extraArg

    def test_something(self):
        print(self.myExtraArg)

# call your test
suite = unittest.TestSuite()
suite.addTest(MyTest('test_something', extraArg))
unittest.TextTestRunner(verbosity=2).run(suite)

Answer 3

To extend with the above comment about unit tests. Unit tests should stand alone in that they have no dependencies outside of their setup and tear down requirements, such as in your case setting up a email. This makes sure that each tests has very specific side effects and reactions to the test. Passing in a parameter defeats this property of unit tests and thus makes them in a sense invalid. Using a test configuration would be the easiest way and-also more proper because again a unit test should never rely on outside information to perform the test. That is for integration tests.

Answer 4

Even if the test gurus say that we should not do it: I do. In some context it makes a lot of sense to have parameters to drive the test in the right direction, for example:

• which of the dozen identical USB cards should I use for this test now?
• which server should I use for this test now?
• which XXX should I use?

For me, the use of the environment variable is good enough for this puprose because you do not have to write dedicated code to pass your parameters around; it is supported by Python. It is clean and simple.

Of course, I'm not advocating for fully parametrizable tests. But we have to be pragmatic and, as I said, in some context you need a parameter or two. We should not abouse of it :)

import os
import unittest


class MyTest(unittest.TestCase):
    def setUp(self):
        self.var1 = os.environ["VAR1"]
        self.var2 = os.environ["VAR2"]

    def test_01(self):
        print("var1: {}, var2: {}".format(self.var1, self.var2))

Then from the command line (tested on Linux)

$ export VAR1=1
$ export VAR2=2
$ python -m unittest MyTest
var1: 1, var2: 2
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

Answer 5

If you want to use steffens21's approach with unittest.TestLoader , you can modify the original test loader (see unittest.py ):

import unittest
from unittest import suite

class TestLoaderWithKwargs(unittest.TestLoader):
    """A test loader which allows to parse keyword arguments to the
       test case class."""
    def loadTestsFromTestCase(self, testCaseClass, **kwargs):
        """Return a suite of all tests cases contained in 
           testCaseClass."""
        if issubclass(testCaseClass, suite.TestSuite):
            raise TypeError("Test cases should not be derived from "\
                            "TestSuite. Maybe you meant to derive from"\ 
                            " TestCase?")
        testCaseNames = self.getTestCaseNames(testCaseClass)
        if not testCaseNames and hasattr(testCaseClass, 'runTest'):
            testCaseNames = ['runTest']

        # Modification here: parse keyword arguments to testCaseClass.
        test_cases = []
        for test_case_name in testCaseNames:
            test_cases.append(testCaseClass(test_case_name, **kwargs))
        loaded_suite = self.suiteClass(test_cases)

        return loaded_suite 

# call your test
loader = TestLoaderWithKwargs()
suite = loader.loadTestsFromTestCase(MyTest, extraArg=extraArg)
unittest.TextTestRunner(verbosity=2).run(suite)

Answer 6

I have the same problem. My solution is after you handle with parsing arguments using argparse or another way, remove arguments from sys.argv:

sys.argv = sys.argv[:1]  

If you need, you can filter unittest arguments from main.parseArgs().

Answer 7

This is my solution:

# your test class
class TestingClass(unittest.TestCase):

    # This will only run once for all the tests within this class
    @classmethod
    def setUpClass(cls) -> None:
       if len(sys.argv) > 1:
          cls.email = sys.argv[1]

    def testEmails(self):
        assertEqual(self.email, "my_email@example.com")


if __name__ == "__main__":
    unittest.main()

You could have a runner.py file with something like this:

# your runner.py
loader = unittest.TestLoader()
tests = loader.discover('.') # note that this will find all your tests, you can also provide the name of the package e.g. `loader.discover('tests')
runner = unittest.TextTestRunner(verbose=3)
result = runner.run(tests

With the above code, you should be to run your tests with runner.py my_email@example.com .

Answer 8

Unit testing is meant for testing the very basic functionality (the lowest level functions of the application) to be sure that your application building blocks work correctly. There is probably no formal definition of what does that exactly mean, but you should consider other kinds of testing for the bigger functionality -- see Integration testing . The unit testing framework may not be ideal for the purpose.