Writing unit tests in python

Jul 29, 2015 • 1 minutes to read

A good developer always tests his code. And python being a robust language is very easy to test. Heres a function that adds two numbers and returns their result.

# filename: sum_num.py
def sum(x, y):
    return x + y

Now here is a test case that will test if your function returns the excepted result:

from unittest import TestCase

class TestSum(TestCase):
    
    def test_sum(self):
        from sum_num import sum

        # first store the expected result in a variable
        result = sum(3, 4)

        # check if the result is equal to expected result
        # here the result should be equal to 7.
        self.assertEquals(7, result)

Thats it !

Running your tests

Install the nose2 python package using pip

pip install nose2

This is how my directory is structured:

.
├── sum_num.py
└── tests
   ├── __init__.py
   └── test_sum_num.py

Now when you are in the root directory and run nose2 using the command line (command is nose2), it will check for all the files inside the tests/ directory and look for test cases that have file names that contain in it test and have class names that have the name Test and method names test. So this is how it will look like:

tests/ ---> test_sum_num.py ---> class TestSum ---> method test_sum()

So this is a short run down of how to start running test cases in your projects. You can checkout the official list of assert methods that the unittest.TestsCase class provides here.

Writing unit tests in python

Running your tests

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