Python doctest is easier to use than unittest and pytest. A developer writes the test cases in the documentation and doctest module verifies the results. There are examples in the Fluent Python book that use doctest, but I have not seen them used often.
The Python Module of The Week web site has a page on doctest. It is a nice introduction on how to use doctest. The doctest module is useful in some situations.
Below is a python file which includes a single function. The function has a docstring which also serves as doctest.
#!/usr/bin/env python
# nested_sum adds up elements from a list of lists of integers
# file name: nested_sum.py
def nested_sum(t):
"""
>>> t = [[1, 2], [3], [4, 5, 6]]
>>> nested_sum(t)
21
"""
total = 0
for ti in t:
total += sum(ti)
return total
Run the python file with the following command in bash. Note the -m option
loads doctest module. The -v option represents verbose. Without the -v
option, the command outputs nothing.
python -m doctest -v nested_sum.py
Here are the doctest results:
Trying:
t = [[1, 2], [3], [4, 5, 6]]
Expecting nothing
ok
Trying:
nested_sum(t)
Expecting:
21
ok
1 items had no tests:
nested_sum
1 items passed all tests:
2 tests in nested_sum.nested_sum
2 tests in 2 items.
2 passed and 0 failed.
Test passed.