When Integration Testing Gets Tricky

Certain truly external systems may be difficult to integrate into tests. This is because they have side effects in the real world that cannot be undone: A financial transaction, an email send, physically moving a paint robot. Before you give up and sidestep them in your testing, look around for solutions.

Many external systems will have a documented way to use them in an integration test. Payment processors often have test credit card numbers, and test users with test email accounts can be set up for testing delivery. The closer integration tests are to real-world interactions the more likely they are to catch problems and provide real value.

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