jest mock mockname

1test("mockFn.mockReset", () => {
2  const mockFn = jest.fn().mockImplementation(() => 43);
3  const MockClass = jest.fn();
4
5  new MockClass();
6  expect(mockFn()).toBe(43);
7
8  expect(mockFn.mock.calls).toHaveLength(1);
9  expect(MockClass.mock.instances).toHaveLength(1);
10
11  mockFn.mockReset();
12  MockClass.mockReset();
13
14  new MockClass();
15  expect(mockFn()).toBeUndefined();
16
17  expect(mockFn.mock.calls).toHaveLength(1);
18  expect(MockClass.mock.instances).toHaveLength(1);
19});

1import Foo from './Foo';
2import Bar from './Bar';
3
4jest.mock('./Bar');
5
6describe('Foo', () => {
7  it('should return correct foo', () => {
8    // As Bar is already mocked,
9    // we just need to cast it to jest.Mock (for TypeScript) and mock whatever you want
10    (Bar.prototype.runBar as jest.Mock).mockReturnValue('Mocked bar');
11    const foo = new Foo();
12    expect(foo.runFoo()).toBe('real foo : Mocked bar');
13  });
14});
15
16
17

1test("mockName", () => {
2  const mockFn = jest.fn().mockName("mockedFunction");
3  mockFn(); // comment me
4  expect(mockFn).toHaveBeenCalled();
5});

1test("mock.calls", () => {
2  const mockFn = jest.fn();
3  mockFn(1, 2);
4
5  expect(mockFn.mock.calls).toEqual([[1, 2]]);
6});