Jest - KeynesYouDigIt/Knowledge GitHub Wiki

beforeEach(() => {})

describe.only("behavior", () => {
  it("should do something", () => {
    expect().toBeTruthy()
  })
  it("should do something", done => {
    expect().toBeTruthy()
    done()
  })
})

Flags

• .not
• .resolves

Assertions

• .toBe(referenceEquality)
• .toEqual(valueEquality)
• .toBeTruthy() / .toBeFalsy()
• .toBeNull() / .toBeDefined(), / .toBeUndefined()
• .toBeGreaterThan(), toBeGreaterThanOrEqual()
• .toBeCloseTo() (fixes floating point math)
• .toMatch(/regex/)
• .toContain()
• .anything() / .any(Type)

Mocks

• const mockedFunction = jest.fn()
• const mockedFunction = jest.fn(someParameter => "some value")
• .toHaveBeenCalled
• .toHaveBeenCalledWith
• .mockReturnValue() / .mockReturnValueOnce()
• .mockResolvedValue() / .mockResolvedValueOnce()
• jest.mock("axios")

Timers

• jest.useFakeTimers()
• jest.runAllTimers()
• jest.advanceTimersByTime(1000)