using jest spyon code example
Example 1: jest spyon
const spy = jest.spyOn(video, 'play');
const spy = jest.spyOn(video, 'play', 'get');
Example 2: jest spy on class method
class MyClass {
methodOne() {
return 1;
}
methodTwo() {
return 2;
}
}
module.exports = MyClass;
test('spy using class method', () => {
const result = new MyClass()
const spy = jest.spyOn(result, 'methodOne')
result.methodOne()
expect(spy).toHaveBeenCalled()
expect(result.methodOne()).toBe(1)
spy.mockReturnValueOnce(12)
expect(result.methodOne()).toBe(12)
})