jest spyon
// jest.spyOn(object, methodName)
const spy = jest.spyOn(video, 'play');
// jest.spyOn(object, methodName, accessType?)
const spy = jest.spyOn(video, 'play', 'get'); // we pass 'get'//class.js
class MyClass {
methodOne() {
return 1;
}
methodTwo() {
return 2;
}
}
module.exports = MyClass;
// class.test.js
test('spy using class method', () => {
const result = new MyClass()
const spy = jest.spyOn(result, 'methodOne')
result.methodOne()
// check class method is call or not
expect(spy).toHaveBeenCalled()
// expect old value
expect(result.methodOne()).toBe(1)
// expect new value
spy.mockReturnValueOnce(12)
expect(result.methodOne()).toBe(12)
})
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