How to use Coverage in Django

Django, Python

When you are developing a large project, it is possible to accidentally forget some parts of the code that need to be tested. Coverage.py is a python tool to help you with this.

Installation

Use pip or easy_install as you like

pip install coverage 

Starting and uninstalling

To run in a Django project, use the command:

overage run --source='.' manage.py test the-app-you-want-to-test

This command will fill in ".coverage" which is located in COVERAGE_FILE and then you can see the results or report. If you need to delete the received data, use the command:

coverage erase

For one file

If you only want to test Python code, then you need to do:

coverage run your_program.py arg1 arg2 arg3

There are several additional options that you can look at link .
You can learn about templates in the plugins section .

View result

If you want to display results on the command line:

coverage report

For clearer and more convenient reports:

coverage html

To know exactly what part of your code is covered by tests, use the following command:

coverage annotate -d directory-where-to-put-annotated-files

The program will generate the same source code file with additional syntax:

- A line with ">" means that it has been executed.

- A line starting with "!" means that it was not executed.

- A line starting with "-" means that the line has been excluded from the coverage statistics.

Good level of coverage

Good coverage is usually 90%. However, if the result is 100%, this may be a bad signal, since it may be a matter of coverage, and not the quality of the tests.

A few tips:

- Be careful with the quality of your tests.

- Don't slow down your developer speeds for the sake of coverage.

- Use coverage to find unverified code and decide if it deserves coverage.

Exclude code

Sometimes we need to exclude some code that doesn't need coverage. There are several options:

- Specifying files to exclude and skip in .coveragerc.

- Writing in one line of the comment block.

 # pragma: no cover

For example, if you want to exclude generated code from coverage because it must be supported by the generation tool:

def generated_code():   # pragma: no cover
   do_something()

More info at Coverage.py documentation.