Python is a great choice for beginners because it’s widely used and easy to learn. But it can be hard to learn without guidance. PyTest is a testing framework that makes writing tests easy, and it can make testing even easier by making it easy to test individual functions or entire modules.
In this post, we’ll show how to use PyTest to test Python code. We’ll use Python 3.5 and PyTest 3.7.1.
Pytest is an open-source testing tool that allows you to test Python code quickly and easily. It provides a way to test individual functions, classes, modules, and packages. Pytest runs your tests at the command line, and it can automatically generate reports about the results.
You can test code using pytest in several ways. For example, you can write tests as if you were testing them manually, then run them as part of the unit testing cycle. Or, you can write tests as if you were writing automated regression tests, then run them at the end of your normal development cycle.
The Basics – PyTest
Before we start, let’s take a look at the basics of PyTest. A module is a collection of functions or classes, but a function is something that performs a task. To test a module, you must first write a set of tests that exercise each function or class in the module. These tests are known as unittests because they test individual functions.
To write a test for a function, you create a test case and then call the function. This test case is known as a test function. For example, suppose we have a function that calculates the volume of a box:
def volume(height, width, depth):
"""Calculate the volume of a box with given dimensions."""
return height * width * depth
To test this function, we need to write a test that exercises the function. To do that, we create a test function that calls the function we want to test, like so:
import pytest
def test_volume():
pytest.assertEqual(volume(3, 5, 2), 15)
If the test passes, we’re satisfied that the function is working correctly. If the test fails, we have discovered a bug in the code.
How to test Python code with pytest
To test Python code, start by creating a test script. A test script consists of a test function that defines the behavior you want to test and a set of fixtures that define the environment in which the test should run.
When running tests, pytest compares the output of the test function with the output of the fixtures. If there is no difference between the output of the test and the output of the fixtures, then the test passes. If there is a difference, then the test fails.
In addition to comparing the output of the fixtures and the output of the test function, pytest can compare the output of the fixtures and the input of the test function.
For example, suppose you have written a function called print_foo that prints a message. Then you can write a test that compares the output of the function with the input of the function.
pytest.raises(TypeError)
print_foo('hello')
def print_foo(x):
print x
def test_print_foo():
assert 'hello' == print_foo('hello')
How to test Python code with pytest:Outline
Writing a test script
A test script consists of a test function that defines the behavior you want to test and a set of fixtures that define the environment in which the test should run.
When running tests, pytest compares the output of the test function with the output of the fixtures. If there is no difference between the output of the test and the output of the fixtures, then the test passes. If there is a difference, then the test fails.
In conclusion, PyTest provides a number of tools for analyzing code coverage. They are helpful to ensure that the tests are being run and are testing the correct features. The code coverage tool is useful when analyzing whether or not a new feature has been fully tested, and to assess test coverage across modules.
