Mu’s Test Suite

We have tests so we can make changes with confidence.

We use several different sorts of test:

  • PyFlakes for checking for errors in our code.

  • pycodestyle for making sure our coding style conforms with most of the conventions of PEP8.

  • PyTest as a framework for writing our unit tests.

  • Coverage for checking the coverage of our unit tests.


We currently have 100% test coverage.

It means every line of code in Mu has been exercised by at least one unit test. We would like to keep it this way!

We can’t claim that Mu is bug-free, but we can claim that we’ve expressed an opinion about how every line of code should behave. Furthermore, our opinion of how such code behaves may NOT be accurate or even desirable. ;-)

In addition, we regularly make use of the excellent LGTM online code quality service written, in part, by friend-of-Mu, Dr.Mark Shannon.

Running the Tests

Running the tests couldn’t be simpler: just use the make command:

$ make check

This will run ALL the tests of each type.

To run specific types of test please try: make pyflakes, make pycodestyle, make test or make coverage.


The test suite will only work if you have installed all the requirements for developing Mu.

Please see Developer Setup for more information on how to achieve this.

Writing a New Test

All the unit tests are in the tests subdirectory in the root of Mu’s repository. The tests are organised to mirror the code structure of the application itself. For example, the tests for the mu.modes.base namespace are in the file.

As mentioned above, we use PyTest as a framework for writing our unit tests. Please refer to their extensive documentation for more details.

In terms of our expectation for writing a test, we expect it to look something like the following:

def test_MyClass_function_name_extra_info():
    This is a description of the INTENTION of the test. For
    example, we may want to know why this test is important,
    any special context information and even a reference to a
    bug report if required.
    assert True  # As per PyTest conventions, use simple asserts.

We also expect your test code to pass PyFlakes and PEP checks. If in doubt, don’t hesitate to get in touch and ask.