Python Unit test module throws "ModuleNotFoundError: No module named 'tests.test_file'"

Question

I’m trying to execute a test case for a project I’ve been working on. I used to successfully execute the unit tests earlier but it errors out now. I know for sure that there have been no updates to any libraries or change in the Path. I tried to look at the source code and figure out why it’s erroring out but no luck yet. Any help on this would be appreciated.

Python version – 3.7.1

Sample Code below

import unittest

class MyTestCase(unittest.TestCase):

def test_dummy(self):
    self.assertEqual(2+2,4)

I used the following command in cmd to execute the test.

C:UsersYadadaDesktoprepomwemwe>python -m unittest teststest_file.py

My folder structure is

 MWE -|
      |_tests - |
                |_test_file.py

The expected output is the test being executing successfully because it’s a straightforward one. But I end up getting the following error

strclass
ERROR: test_file (unittest.loader._FailedTest)
----------------------------------------------------------------------
ImportError: Failed to import test module: test_file
Traceback (most recent call last):
  File "C:UsersyadadaAppDataLocalContinuumanaconda3libunittestloader.py", line 156, in loadTestsFromName
    module = __import__(module_name)
ModuleNotFoundError: No module named 'tests.test_file'


----------------------------------------------------------------------
Ran 1 test in 0.001s

Asked By: Bee

||

Source

Answer 1

The issue got resolved after placing an empty __init__.py file in the tests folder.

For a better explanation about why it worked, refer to What is __init__.py for?

Thanks, @aws_apprentice for the help.

Answered By: Bee

Answer 2

With PyCharm 2020.2 the "ModuleNotFoundError: No module named" error can also happen when running a unit test in a sub folder which imports a module from a parent folder under test. PyCharm is taking by default the script path for executing the test which fails e.g. with this error:

ModuleNotFoundError: No module named '/home/foobar/projects/foo/mypythonproject/moduleundertest'

The solution is to edit the run configuration of the unit test and change the Unittests Target from "Script path" to "Module name".

Answered By: k_o_

Answer 3

The solution for me was to add:

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

to the bottom of my test file.

I was then able to run:

python -m <test-file>

Removing the .py suffix from my python -m command was also required:

See this answer for details.

Answered By: tjheslin1

Answer 4

The reason is some library is using the package name already, see:
this stack overflow question about reserved package names

To understand the poblem: rename the tests package to tests_package package. (test is also a reserved package name)

Before:

MWE -|
     |- tests -|
               |- test_file.py

After:

MWE -|
     |- tests_package -|
                       |- test_file.py

(Since python 3.3 the __init__.py is not required.)

Then running python -m unittest tests_packagetest_file.py

Using a "venv" would solve it for tests package name but not for test

Probably an even more pythonic solution would be to not have your project run in "root" by giving it a unique module name, releasing you from the requirement to have a package name unused by python libraries for the tests directory.
example:

GitFolderOfProject -|
                    |- MWE -|
                            |- tests -|
                                      |- test_file.py

Then running the tests from the "GitFolderOfProject" as python -m unittest MWEteststest_file.py

Answered By: Eaton Emmerich

Answer 5

This is a simple setup magic.

First things first – in PyCharm:

Right-click on folder (in the project tree) with tests – mark this folder as "tests folder".
Right-click on folder (in the project tree) with sources – mark this folder as "sources folder".
Remove bad "Run configuration" (or don’t remove, you choose).
Right click on on folder with tests (already marked as the "tests folder") – choose "run".

This is all. Really simple. Logical. It took me about an hour to find it out.

Answered By: VOLTAGE SOURCE

Python Unit test module throws "ModuleNotFoundError: No module named 'tests.test_file'"

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