JEST Framework Full Crash Course | Java Script Unit Testing

Install the jest framework in your project by creating package.json with npm init and installing jest as a dev dependency with npm install --save-dev jest, and review node_modules for packages.

Set up a nodejs project with jest, add a test script in package.json, create a sum function, and write a .test.js file using require and test to verify the sum.

Explore how to create and run api tests in jest using json file data and a mysql database, including setting up routes, validating responses and status codes.

Discover how to test code with Jest using the expect function and matchers to compare actual values with expected results, including modifiers and extended utilities.

Explore jest matchers to be and to be close to for strict and approximate numeric comparisons, with test setup, describe blocks, and precision handling in unit tests.

Learn how to use Jest matchers to verify function calls, including toHaveBeenCalled, toHaveBeenCalledTimes, toHaveBeenCalledWith, last and nth call checks, with practical examples.

Explore jest matchers for returns, including to have return, to have return times, to have returned with, and to have last return with, using mock functions and nth-call checks.

Explore how to use toHaveLength to test string and array lengths, and toHaveProperty to validate properties, including nested ones, in Jest unit tests.

Learn how to use Jest matchers toBeDefined, toBeUndefined, toBeFalsy, and toBeTruthy to verify function return values and handle truthy and falsy cases.

Explore Jest matchers for arrays, strings, and objects, including toContain and toContainEqual. Learn toEqual and toStrictEqual for full object equality and undefined property validation.

Explore jest matchers for strings and objects, using toMatch with regular expressions to validate partial or full strings, and toMatchObject to verify a subset of object properties.

Use Jest's toThrow matcher to verify that a function throws an error, test error messages, substrings, and exact messages.

Explore the Jest framework modifiers like .not, .resolves, and .rejects, and learn how to apply them with matchers to test asynchronous code.

Explore asymmetric matchers in Jest, including expect.anything and expect.any, to validate values without exact literals. See practical examples with mock functions and calls.

Learn how to use expect.closeTo in Jest, an asymmetric matcher, to compare floating point numbers in objects and arrays with a specified precision.

Learn how to use expect.arrayContaining and expect.objectContaining to assert that received arrays or objects include subset values. The lecture demonstrates passing and failing tests with these asymmetric matchers.

Learn how to use Jest asymmetric matchers for string containment and string matching, including expect.stringContaining and expect.stringMatching, with examples like 10% discount and 5% discount.

Explore how to create and use custom matchers in Jest, including a to be equal shapes example, and set up Jest to extend expect with these new matchers.

Master handling asynchronous code in jest using promise, async/await, callbacks, and dot resolves/dot rejects, with practical tests of sum and search filter functions.

Learn how to count assertions and matchers in jest tests using expect.assertions and expect.hasAssertions, with examples that demonstrate string equality and counting matcher calls.

Learn how to use Jest hooks to build a watch plugin that triggers test runs on file changes or key presses, with examples of defining prompts, keys, and actions.

Use jest hooks before all, after all, before each, and after each within a describe block to run and log test execution.

Explore jest global methods, including describe, test, describe.each, test.concurrent, and describe.not, and learn to run data-driven tests without imports in the global environment.

Test snapshots by rendering a UI component, capturing a snapshot, and comparing it to a reference or inline snapshot. Update snapshots with npm run test -- -u as needed.

Learn how mock functions replace dependencies in jest to test functions in isolation. Create and use mocks with jest.fn, set mock names, simulate return values, and verify calls and outcomes.

Discover Jest cli options to run tests from the command line, explore the full list of commands in the official cli docs, and practice using different command-line options.