Function expect

not

addSnapshotSerializer

• addSnapshotSerializer(serializer: Plugin_2): void

• Adds a module to format application-specific data structures for serialization.

  Parameters

  • serializer: Plugin_2

  Returns void

any

• any(classType: any): any

• Matches anything that was created with the given constructor. You can use it inside toEqual or toBeCalledWith instead of a literal value.

  Parameters

  • classType: any

  Returns any

  Example

  function randocall(fn) {
    return fn(Math.floor(Math.random() * 6 + 1));
  }
  
  test('randocall calls its callback with a number', () => {
    const mock = jest.fn();
    randocall(mock);
    expect(mock).toBeCalledWith(expect.any(Number));
  });
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anything

• anything(): any

• Matches anything but null or undefined. You can use it inside toEqual or toBeCalledWith instead of a literal value. For example, if you want to check that a mock function is called with a non-null argument:

  Returns any

  Example

  test('map calls its argument with a non-null argument', () => {
    const mock = jest.fn();
    [1].map(x => mock(x));
    expect(mock).toBeCalledWith(expect.anything());
  });
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arrayContaining

• arrayContaining<E = any>(arr: E[]): any

• Matches any array made up entirely of elements in the provided array. You can use it inside toEqual or toBeCalledWith instead of a literal value.

  Optionally, you can provide a type for the elements via a generic.

  Type Parameters

  • E = any

  Parameters

  • arr: E[]

  Returns any

assertions

• assertions(num: number): void

• Verifies that a certain number of assertions are called during a test. This is often useful when testing asynchronous code, in order to make sure that assertions in a callback actually got called.

  Parameters

  • num: number

  Returns void

closeTo

• closeTo(num: number, numDigits?: number): any

• Useful when comparing floating point numbers in object properties or array item. If you need to compare a number, use .toBeCloseTo instead.

  The optional numDigits argument limits the number of digits to check after the decimal point. For the default value 2, the test criterion is Math.abs(expected - received) < 0.005 (that is, 10 ** -2 / 2).

  Parameters

  • num: number
  • OptionalnumDigits: number

  Returns any

extend

• extend(obj: ExpectExtendMap): void

• You can use expect.extend to add your own matchers to Jest.

  Parameters

  • obj: ExpectExtendMap

  Returns void

getState

• getState(): MatcherState & Record<string, any>

• Returns MatcherState & Record<string, any>

hasAssertions

• hasAssertions(): void

• Verifies that at least one assertion is called during a test. This is often useful when testing asynchronous code, in order to make sure that assertions in a callback actually got called.

  Returns void

objectContaining

• objectContaining<E = {}>(obj: E): any

• Matches any object that recursively matches the provided keys. This is often handy in conjunction with other asymmetric matchers.

  Optionally, you can provide a type for the object via a generic. This ensures that the object contains the desired structure.

  Type Parameters

  • E = {}

  Parameters

  • obj: E

  Returns any

setState

• setState(state: object): void

• Parameters

  • state: object

  Returns void

stringContaining

• stringContaining(str: string): any

• Matches any received string that contains the exact expected string

  Parameters

  • str: string

  Returns any

stringMatching

• stringMatching(str: string | RegExp): any

• Matches any string that contains the exact provided string

  Parameters

  • str: string | RegExp

  Returns any