Test Doubles

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We know tests contain E2E, Integration, and Unit tests. We use test doubles when we have indirect inputs (like queries), indirect outputs (like sending events to events stream or when you call API), or slow tests (when you call the server or the database or over the network). These mocks can have different types:

Mocks: This is an object that you record what you do to it and record data and you can verify what has been done to the mock object. It’s more for testing behaviors.
Stubs: Are simple and they provide indirect inputs for the system. It’s more for testing the state. Stubs never fail a test but mocks can (like out of order process). You assert against mocks but not against Stubs.
Spies: They have a Call log, a Response list, and State Access. They are stubs but with a call log and they intercept real pieces of code.
Dummies: Just values holder
Fakes: replace real implementation with a fake implementation to simulate situations or for making tests faster. They

Note: across the community, the naming might be different and not unified. It’s enough to get the idea about them and use the proper construct