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The Hidden Cost of Test Inheritance
- Adam Johnson's blog post discusses the hidden cost of using test inheritance in Python.
- The post introduces a pattern of writing reusable test logic in a base class and subclassing it for testing different objects, aiming to reduce duplicated code.
- While the intention is to follow the DRY principle, the approach results in fragility, confusion, and inefficiency in maintaining tests.
- Using inheritance for tests can lead to IDE and development experience issues, making it challenging to debug failing tests.
- In cases of CI failures, identifying the source of the failure becomes difficult due to the hidden nature of methods inherited through subclassing.
- The article suggests that the inheritance-based approach may make sense only in specific scenarios where many classes implement the same interface and under certain conditions.
- An alternative approach recommended is parametrization, with examples provided in both pytest and unittest styles.
- With parametrization, tests are explicit, failures are clear, and debugging becomes more straightforward.
- Using the pytest style of parametrization allows for better readability and debugging capabilities compared to the unittest style, which is considered less ideal.
- The final verdict of the article is to prioritize clear test failures, easy debugging, and long-term readability over reducing code duplication through complex inheritance.
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