Pytest Fundamentals for Data Engineers

Short summary

A practical tutorial covering pytest fundamentals for data engineers, including the Arrange-Act-Assert pattern, exception testing with pytest.raises, expected-failure markers, and mocking external dependencies like S3. Code examples demonstrate testing pure transformations, schema validation, and infrastructure-isolated unit tests. The guide targets engineers building reliable data pipelines who need to catch regressions before production.

• •Core pytest pattern: Arrange, Act, Assert for testing pipeline transformations
• •Exception testing with pytest.raises and match parameter for precise error validation
• •Mocking external dependencies (S3, databases) using unittest.mock to keep tests fast and deterministic

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