Coverage in Python

1. Install the pytest Plugin for Coverage in Python
2. Use the pytest Plugin for Statement Coverage in Python

This article will discuss the uses of coverage in Python for testing the python program execution.

Code coverage means monitoring the code to check which part has been executed and has not. For this purpose, we use the pytest plugin in Python.

Install the pytest Plugin for Coverage in Python

To use this plugin, we should install it first using the following command.

#Python 3.x
pip install pytest-cov

Use the pytest Plugin for Statement Coverage in Python

Statement coverage, also known as line coverage, is white box testing. All the executable statements are executed at least once to ensure running without any error.

Statement coverage is the default coverage used by the coverage module in Python. It calculates the coverage based on the following formula.

Statement Coverage = {Number of statements executed / Total number of statements in the code}  * 100

We will create a module, CovModule, to run the coverage in our example. This will consist of the actual code to cover.

We will make another Python file, in which we will import this module and call the function.

In the following code, if the value of a is greater than or equal to b, then the if block will execute, and the else block will skip. So, coverage will be 75 percent.

Therefore, either if or else will execute in any situation. But the overall coverage of the code will be 100 percent.

# Python 3.x
# CovModule.py
def check(num1, num2):
    if num1 <= num2:
        print("if executed")
    else:
        print("else executed")

# Python 3.x
# test.py
from CovModule import check

check(2, 3)

Finally, we will run the following command to run the code coverage and generate its report. We will see the module name, the total number of statements, missed statements and executed statements in the report.

pytest --cov CovModule test.py

Output: