use jest mock to get html with js function code example

Example 1: jest mock mockname

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

Example 2: test function that call a function javascrip

var bar = require('./bar');

var Foo = module.exports = function () {
  this.bar();
  this.barModule();
};
Foo.prototype.bar = function () {};
Foo.prototype.barModule = bar; // setting here as barModule