5+ Pytest 使い方 For You

GitHub pytestdev/pytest The pytest framework makes it easy to write from github.com

Introduction

Pytest has become one of the most popular testing frameworks for Python developers. It is easy to use, efficient, and has a lot of great features that make testing a breeze. In this article, we will explore the basics of Pytest and how to use it to write effective tests for your Python code.

What is Pytest?

Pytest is a testing framework for Python that allows developers to write simple and scalable tests. It provides a lot of useful features such as fixtures, parameterization, and plugins that make testing much easier and fun. Pytest is a great alternative to the built-in unittest library in Python.

Getting Started with Pytest

The first step to using Pytest is to install it. You can install Pytest using pip:

pip install pytest

Once you have Pytest installed, you can start writing your first test.

Writing Your First Test

Let's create a simple function that adds two numbers and write a test for it:

def add_numbers(a, b): return a + b def test_add_numbers(): assert add_numbers(2, 3) == 5

In this test, we are using the assert statement to check if the result of add_numbers(2, 3) is equal to 5. If the assertion fails, Pytest will raise an AssertionError.

Using Fixtures

Fixtures are a powerful feature of Pytest that allow you to define reusable code that can be used in multiple tests. A fixture is a function that returns a value that can be used in a test. Let's create a fixture that returns a list of numbers:

import pytest @pytest.fixture def numbers(): return [1, 2, 3, 4, 5]

We can now use this fixture in our tests:

def test_sum(numbers): assert sum(numbers) == 15

In this test, we are using the numbers fixture to get a list of numbers and then using the sum function to calculate the sum of the numbers. This is just a simple example, but fixtures can be used for more complex scenarios such as setting up a database connection, creating temporary files, or mocking external APIs.

Parameterization

Parameterization is a feature of Pytest that allows you to run the same test with different inputs. This is useful when you want to test a function with multiple inputs or test different scenarios. Let's create a test that uses parameterization:

 import pytest @pytest.mark.parametrize("a, b, expected_result", [ (2, 3, 5), (4, 5, 9), (10, 20, 30) ]) def test_add_numbers(a, b, expected_result): assert add_numbers(a, b) == expected_result

In this test, we are using the @pytest.mark.parametrize decorator to define multiple inputs for the test. The test will run three times, once with each set of inputs, and Pytest will check if the expected result matches the actual result.

Plugins

Pytest has a lot of plugins that can be used to extend its functionality. Plugins can be used for things like generating test reports, measuring code coverage, or running tests in parallel. To use a plugin, you need to install it and then enable it in your Pytest configuration file. Let's install and enable the pytest-html plugin:

pip install pytest-html

Now, we can enable the plugin by adding the following to our Pytest configuration file:

[pytest] addopts = --html=report.html

When we run our tests, the plugin will generate an HTML report that shows the results of our tests.

Conclusion

Pytest is a powerful testing framework for Python that can make testing easier and more fun. In this article, we covered the basics of Pytest and how to use it to create effective tests. We explored fixtures, parameterization, and plugins, which are just a few of the many features that Pytest has to offer. By using Pytest, you can ensure that your Python code is reliable and robust.