Jest Matchers: Asserting Values in Your Tests
Jest matchers are assertion functions that check if a value meets a condition. You use them with `expect()` to verify function outputs, object properties, or promise states.
Jest matchers are assertion functions that validate if your code's output meets conditions. Think of `expect(value).toBe(expected)` as asking, "Is the value my code produced what I think it should be?". You use them to check primitives (`.toBe`), objects (`.toEqual`), or promise states (`.resolves`). The footgun: always put your code's output in `expect()` and the correct value in the matcher. Swapping them makes failure messages confusing and unhelpful.
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