如何用Pytest测试Python代码

Pytest是Python中简单强大的测试工具，安装后按命名规则自动发现测试文件。编写以test_开头的函数进行断言测试，使用@pytest.fixture创建可复用的测试数据，通过pytest.raises验证异常，支持运行指定测试和多种命令行选项，提升测试效率。

Testing Python code with pytest is simple, powerful, and widely used in the Python community. It helps you write clean, maintainable tests with minimal boilerplate. Here’s how to get started and use it effectively.

Install and Set Up Pytest

First, install pytest using pip:

Once installed, you can run tests from your project root. Pytest automatically discovers test files and functions following naming conventions.

By default, it looks for files named:

• test_*.py
• *_test.py

Inside these files, it runs functions starting with test_.

Write Your First Test

Create a file called test_sample.py with a simple function and test:

Run the test in your terminal:

You’ll see output showing how many tests passed or failed.

Use Fixtures for Reusable Setup

Pytest fixtures let you define reusable setup logic. For example, if you need a database connection or test data:

The sample_data fixture is injected into any test that requests it by parameter name.

Test Exceptions and Edge Cases

To check that code raises expected exceptions, use pytest.raises:

Run Specific Tests and Use Options

You can run specific tests using patterns:

• pytest test_sample.py – run all tests in a file
• pytest test_sample.py::test_add – run one test function
• pytest -v – show verbose output
• pytest -x – stop after first failure
• pytest --tb=short – shorten traceback

Basically, pytest makes testing easy once you follow the naming rules and learn to use assertions and fixtures. It handles most of the plumbing so you can focus on writing meaningful tests.

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