Jest

Painless JavaScript Unit Testing

• Familiar Approach: Built on top of the Jasmine test framework, using familiar expect(value).toBe(other) assertions

• Mock by Default: Automatically mocks CommonJS modules returned by require(), making most existing code testable

• Short Feedback Loop: DOM APIs are mocked and tests run in parallel via a small node.js command line utility

Getting Started

Check out the Getting Started tutorial. It's pretty simple!

API

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The jest object

• jest.autoMockOff()

• jest.autoMockOn()

• jest.clearAllTimers()

• jest.dontMock(moduleName)

• jest.genMockFromModule(moduleName)

• jest.genMockFunction()

• jest.genMockFn()

• jest.mock(moduleName)

• jest.runAllTicks()

• jest.runAllTimers()

• jest.runOnlyPendingTimers()

• jest.setMock(moduleName, moduleExports)

Mock functions

• mockFn.mock.calls

• mockFn.mock.instances

• mockFn.mockClear()

• mockFn.mockImplementation(fn)

• mockFn.mockImpl(fn)

• mockFn.mockReturnThis()

• mockFn.mockReturnValue(value)

• mockFn.mockReturnValueOnce(value)

Config options

• config.cacheDirectory [string]

• config.collectCoverage [boolean]

• config.collectCoverageOnlyFrom [object]

• config.globals [object]

• config.moduleFileExtensions [array]

• config.modulePathIgnorePatterns [array]

• config.rootDir [string]

• config.scriptPreprocessor [string]

• config.setupEnvScriptFile [string]

• config.setupTestFrameworkScriptFile [string]

• config.testDirectoryName [string]

• config.testFileExtensions [array]

• config.testPathDirs [array]

• config.testPathIgnorePatterns [array]

• config.testPathPattern [string]

• config.unmockedModulePathPatterns [array]

Globally injected variables

• afterEach(fn)

• beforeEach(fn)

• describe(name, fn)

• it(name, fn)

• it.only(name, fn) executes only this test. Useful when investigating a failure

• jest

• pit(name, fn) helper for promises

• require(module)

• require.requireActual(module)

• xdescribe(name, fn)

• xit(name, fn)

expect(value)

• .not inverse the next comparison

• .toThrow(?message)

• .toBe(value) comparison using ===

• .toEqual(value) deep comparison. Use jasmine.any(type) to be softer

• .toBeFalsy()

• .toBeTruthy()

• .toBeNull()

• .toBeUndefined()

• .toBeDefined()

• .toMatch(regexp)

• .toContain(string)

• .toBeCloseTo(number, delta)

• .toBeGreaterThan(number)

• .toBeLessThan(number)

• .toBeCalled()

• .toBeCalledWith(arg, um, ents)

• .lastCalledWith(arg, um, ents)

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