Our codebase is far from perfect, but the goal is to steadily improve our coverage over time. To do this, we wrote a tool called diff-cover that will report which lines in your branch are not covered by tests, while ignoring other lines in the project that may not be covered. Using this tool, we can ensure that pull requests have a very high percentage of test coverage – and ideally, they increase the test coverage of existing code, as well.
To check the coverage of your pull request, just go to the top level of the edx-platform codebase and run:
$ paver coverage
This will print a coverage report for your branch. We aim for a coverage report score of 95% or higher. We also encourage you to write acceptance tests as your changes require.