Pytest: Mocking - why?

• Testing environment that does not depend on external systems.

• Faster tests (mock remote calls, mock whole databases, etc.)

• Fake some code/application/API that does not exist yet.

• Test error conditions in a system not under our control.

• TDD, unit tests

• Spaghetti code

• Simulate hard to replicate cases

• 3rd party APIs or applications