When you're writing tests, you often need to check that values meet certain conditions. expect gives you access to a number of "matchers" that let you validate different things.

For additional Jest matchers maintained by the Jest Community check out jest-extended.

Reference

• expect(value)
• expect.extend(matchers)
• expect.anything()
• expect.any(constructor)
• expect.arrayContaining(array)
• expect.assertions(number)
• expect.hasAssertions()
• expect.not.arrayContaining(array)
• expect.not.objectContaining(object)
• expect.not.stringContaining(string)
• expect.not.stringMatching(string | regexp)
• expect.objectContaining(object)
• expect.stringContaining(string)
• expect.stringMatching(string | regexp)
• expect.addSnapshotSerializer(serializer)
• .not
• .resolves
• .rejects
• .toBe(value)
• .toHaveBeenCalled()
• .toHaveBeenCalledTimes(number)
• .toHaveBeenCalledWith(arg1, arg2, …)
• .toHaveBeenLastCalledWith(arg1, arg2, …)
• .toHaveBeenNthCalledWith(nthCall, arg1, arg2, ….)
• .toHaveReturned()
• .toHaveReturnedTimes(number)
• .toHaveReturnedWith(value)
• .toHaveLastReturnedWith(value)
• .toHaveNthReturnedWith(nthCall, value)
• .toBeCloseTo(number, numDigits)
• .toBeDefined()
• .toBeFalsy()
• .toBeGreaterThan(number)
• .toBeGreaterThanOrEqual(number)
• .toBeLessThan(number)
• .toBeLessThanOrEqual(number)
• .toBeInstanceOf(Class)
• .toBeNull()
• .toBeTruthy()
• .toBeUndefined()
• .toBeNaN()
• .toContain(item)
• .toContainEqual(item)
• .toEqual(value)
• .toHaveLength(number)
• .toMatch(regexpOrString)
• .toMatchObject(object)
• .toHaveProperty(keyPath, value)
• .toMatchSnapshot(propertyMatchers, snapshotName)
• .toMatchInlineSnapshot(propertyMatchers, inlineSnapshot)
• .toStrictEqual(value)
• .toThrow(error)
• .toThrowErrorMatchingSnapshot()
• .toThrowErrorMatchingInlineSnapshot()