Unit testing concepts and common Jest matchers and mocking patterns for testing JavaScript code.
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- What is unit testing?
- Testing individual functions or modules in isolation to verify they work correctly
- What does the arrange, act, assert pattern mean?
- Set up test data and state (arrange), execute the code (act), verify the result (assert)
- What is a test suite?
- A collection of related test cases grouped together
- What is a test case?
- A single test that checks one specific behavior or output
- What does Jest's toBe() matcher test?
- Strict equality (===) between two values
- What does Jest's toEqual() matcher test?
- Deep equality, checking that objects or arrays have the same contents
- What does Jest's toStrictEqual() matcher test?
- Deep equality with strict type checking, including undefined properties
- What does Jest's toContain() matcher test?
- Whether an array contains a specific element or a string contains a substring
- What does Jest's toMatch() matcher test?
- Whether a string matches a given regular expression
- What does Jest's toBeDefined() matcher test?
- Whether a value is not undefined
- What does Jest's toBeNull() matcher test?
- Whether a value is exactly null
- What does Jest's toBeUndefined() matcher test?
- Whether a value is undefined
- What does Jest's toBeTruthy() matcher test?
- Whether a value evaluates to true in a boolean context
- What does Jest's toBeFalsy() matcher test?
- Whether a value evaluates to false in a boolean context
- What does Jest's toThrow() matcher test?
- Whether a function throws an error when called