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Python 201 - Interactively Learn Advanced Concepts in Python 3

Functions of coverage.py

Explore how to use coverage.py to measure the effectiveness of your Python tests and identify untested code. Learn to generate text and HTML reports, interpret coverage results, and improve your unit tests to increase coverage progressively.

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Coverage.py is a 3rd party tool for Python that is used for measuring our code coverage. It was originally created by Ned Batchelder. The term “coverage” in programming circles is typically used to describe the effectiveness of our tests and how much of our code is actually covered by tests. We can use coverage.py with Python 2.6 up to the current version of Python 3 as well as with PyPy.

If you don’t have coverage.py installed, you may do so using pip:

Javascript (babel-node)
pip3 install coverage

Examples of coverage.py

Now that we have coverage.py installed, we need some code to use it with. Let’s use the mymath module that we created earlier in the course. Here’s the code:

Python 3.5
##mymath.py
def add(a, b):
    return a + b
def subtract(a, b):
    return a - b
def multiply(a, b):
    return a * b
def divide(numerator, denominator):
    return float(numerator) / denominator
print(divide(34,5))
print(add(4,5))
print(subtract(3,4))
print(multiply(3,4))

Now we need a test. Here is the code:

Python 3.5
# test_mymath.py
import mymath
import unittest
class TestAdd(unittest.TestCase):
    """
    Test the add function from the mymath library
    """
    def test_add_integers(self):
        """
        Test that the addition of two integers returns the correct total
        """
        result = mymath.add(1, 2)
        self.assertEqual(result, 3)
    def test_add_floats(self):
        """
        Test that the addition of two floats returns the correct result
        """
        result = mymath.add(10.5, 2)
        self.assertEqual(result, 12.5)
    def test_add_strings(self):
        """
        Test the addition of two strings returns the two string as one
        concatenated string
        """
        result = mymath.add('abc', 'def')
        self.assertEqual(result, 'abcdef')
if __name__ == '__main__':
    unittest.main()

Testing the implementation with commands

Let’s test the below example with the commands provided in this lesson and see the ...