pytest basics

The pytest framework makes it easy to write small, readable tests, and can scale to support complex functional testing for applications and libraries.

pytest will run all files of the form test_*.py or *_test.py in the current directory and its subdirectories.

Different ways of using pytest

Run tests in a module

pytest test_mod.py

Run tests in a directory

pytest testing/

Run tests by keyword expressions

pytest -k "MyClass and not method"

This will run tests which contain names that match the given string expression (case-insensitive), which can include Python operators that use filenames, class names and function names as variables.

The example above will run TestMyClass.test_something but not TestMyClass.test_method_simple.

Run tests by node ids

pytest test_mod.py::test_func

Another example specifying a test method in the command line:

pytest test_mod.py::TestClass::test_method

Run tests by marker expressions

pytest -m slow

Will run all tests which are decorated with the @pytest.mark.slow decorator.

Run tests from packages

pytest --pyargs pkg.testing

This will import pkg.testing and use its filesystem location to find and run tests from.

A very basic example:

# content of 1_sample_test.py

def addition(x, y):

return x + y

def test_fail():

assert addition(3, 4) == 5

def test_success():

assert addition(3, 4) == 7