测试带有笑话问题的 ES6 class 方法

Question

My class -

class Course{
  public getFormattedTime(){
    // logic to parse time and return in appropriate format
    // return string
  }
}

According to jest documentation https://jestjs.io/docs/en/es6-class-mocks#automatic-mock , replaces all of its methods with mock functions that always return undefined . So my question is if we're changing all the method return values to undefined then what else there's left to test? I do not want to test how many time this method get's called, I just want to test the actual logic inside the method. Am I missing something here

Answer 1

The goal of testing is to test only and only the function you are targeting. If the function is calling another one, then the second function is supposed to be mocked. The automatic mocking will just create a fake class and each method will return undefined. If you want your methods to return specific values for the testing purpose, then you should have a look on manual mocking. https://jestjs.io/docs/en/es6-class-mocks#manual-mock