Unit testing involves testing individual components of software in isolation to ensure they function correctly. Automated frameworks facilitate this process, which is integral to ensuring that new changes do not disrupt existing functionality. Unit tests also serve as practical documentation and encourage better software design. This testing method boosts development speed and confidence by confirming component reliability before integration. Early bug detection through unit testing also helps minimize future repair costs and efforts.

pytest

Pytest is one of the best tools that you can use to boost your testing productivity for Python codes.

Install

• pip install pytest
• pip install pytest-cov
  • pytest --cov: this returns a coverage of test functions
  • coverage html: log test results in html format

Example

pytest is a libarary for testing. You can run your unit test code by

pytest test_function.py

If you wanna create a directory with several testing files, then just create __init__.py and put it inside the test dir.

• Then, just run pytest test_dir

from calc import square
import pytest

def square(n):
    return n*n

# This is a convention test_{func}
def test_negative():
    assert square(-2)==4
    assert square(-3)==9

def test_positive():
    assert square(2)==4
    assert square(3)==9

def test_zero():
    assert square(0)==0

def test_str():
    # Write down what I expect to get 
    # If it successfully raised the error that I expected
    # Then, it will pass the test
    with pytest.raises(TypeError):
        square("cat")

def main():
    x = int(input("What's x? "))
    print("x squared is", square(x))

if __name__=="__main__":
    main()

• If you want to intentially raise an error, then you can do it by pytest.raises("SomeErrorType")

Note that you can write a warning message like

assert x == <cond>, <MSG>