pytest
Unit Testing with the pytest module
Checking whether pytest is installed
To see whether pytest is installed, try this command:
python3 -m pytest
If pytest is installed, the output will look something like this:
-bash-4.3$ python3 -m pytest
===================================== test session starts ======================================
platform linux -- Python 3.4.3, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
rootdir: /cs/faculty/pconrad/cs8/lab02, inifile:
collected 0 items
================================= no tests ran in 0.03 seconds =================================
-bash-4.3$
On a Mac, it looks like this:
Phills-MacBook-Pro:lab02 pconrad$ python3 -m pytest
====================================== test session starts ======================================
platform darwin -- Python 3.6.2, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
rootdir: /Users/pconrad/cs8/lab02, inifile:
collected 0 items
================================= no tests ran in 0.00 seconds ==================================
Phills-MacBook-Pro:lab02 pconrad$
Installing PyTest on your own system (or for your personal use on CSIL):
If you are working on CSIL, PyTest is likely already installed for you (check using the command shown above).
If not, use this command to install it for your own use:
pip3 install --user pytest
Then try the commands listed above.
Running tests from a single file
To run tests from foo.py, use:
python3 -m pytest foo.py
To run only a particular test called test_bar3, use:
python3 -m pytest foo.py -k test_bar3
The -k does pattern matching, so it can also be a substring of a set of tests you want to run. With suitable naming conventions,
you can have fine control over subsets of the test suite from the command line.
Minimizing output
If you want the output from a set of tests to be compact, and the same each time you run them
(e.g. for use with autograder system such as submit.cs) use the -qq flag:
python3 -m pytest -qq foo.py -k test_bar3
Setting up a simple test
Suppose you have a simple function such as this one that computes the area of a rectangle:
def area_rect(length, width):
return length * width
To set up test cases for this function with pytest, you add functions such as these to area.py
def test_area_rect_1():
assert area_rect(3,5) == 15
def test_area_rect_2():
assert area_rect(2.5,4) == 10.0
You can run the tests by typing either of these commands:
python3 -m pytest area.py
Or simply:
pytest area.py
If the tests pass, it looks like this:
cgaucho$ python3 -m pytest area.py
================================== test session starts ==================================
platform darwin -- Python 3.6.5, pytest-3.5.0, py-1.5.3, pluggy-0.6.0
rootdir: /Users/cgaucho/Downloads, inifile:
plugins: utils-0.0.0
collected 2 items
area.py .. [100%]
=============================== 2 passed in 0.01 seconds ================================
cgaucho$