When testing data pipelines, it is important to consider unit tests to test individual components of the pipeline, integration tests to test the interaction between components, and end-to-end tests to test the complete pipeline from start to finish. This ensures that the pipeline is functioning correctly and meets the required specifications. Option A is correct because unit tests help identify issues with individual components. Option B is correct because integration tests help identify issues with the interaction between components. Option C is correct because end-to-end tests help identify issues with the complete pipeline.