Writing python unit tests inside the actual code

Question

Sometimes I'm writing small utilities functions and pack them as python package.
How small? 30 - 60 lines of python.
And my question is do you think writing the tests inside the actual code is bad? abusing?

I can see a great benefits like usage examples inside the code itself without jumping between files (again from really small projects). Example:

#!/usr/bin/env python
# Actual code
def increment(number, by=1):
    return number += by

# Tests
def test_increment_positive():
    assert increment(1) == 2

def test_increment_negative():
    assert increment(-5) == -4

def test_increment_zero():
    assert increment(0) == 1

The general Idea taken from the monitoring framework riemann which I use, in riemann you write your tests file along with your code link

Sebastian Wozny · Accepted Answer · 2017-02-18 09:57:12Z

5

You can write doctests inside your documentation to indicate how your function should be used:

def increment(number, by=1):
    """ Increments the given number by some other number
    >>> increment(3)
    4
    >>> increment(5,3)
    8
    """
    return number += by

From the documentation:

To check that a module’s docstrings are up-to-date by verifying that all interactive examples still work as documented.

To perform regression testing by verifying that interactive examples from a test file or a test object work as expected.

To write tutorial documentation for a package, liberally illustrated with input-output examples. Depending on whether the examples or the expository text are emphasized, this has the flavor of “literate testing” or “executable documentation”

answered Feb 18, 2017 at 9:57

Sebastian Wozny

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