角度单元测试：此代码值得进行单元测试吗？

Question

I have just began unit testing in angular. I am having a hard time figuring out what should be covered in unit tests in the application. Should I be testing the below code?

If I do I will be essentially be passing a valid value of mode and checking if correct values for various properties of defaultProperties were emitted by this.propertiesSource . Isn't it like writing the same code all over again and more? And this is just one example, application is full of such instances.

If I don't test such things then probably my code coverage will be negligible.

Here is an example of code from component:

 mode: string;
  defaultProperties = {
    editable: this.editable,
    showToolbar: this.showToolbar,
    viewMode: this.viewMode,
    editMode: this.editMode,
    showPopup: this.showPopup,
    formSavedClicked: this.formSavedClicked,
    cancelClicked: this.cancelClicked,
    refresh: this.refresh,
  };
  private propertiesSource = new BehaviorSubject(this.defaultProperties);

Method to be tested:

 setGridMode(mode) {
    this.mode = mode;
    if (mode === "edit") {
      this.propertiesSource.next({
        editable: true,
        showToolbar: true,
        viewMode: false,
        editMode: true,
        showPopup: false,
        formSavedClicked: this.formSavedClicked,
        cancelClicked: this.cancelClicked,
        refresh: false,

      });
    } else if (mode == "save") {
      this.propertiesSource.next({
        editable: false,
        showToolbar: false,
        viewMode: true,
        editMode: false,
        showPopup: false,
        formSavedClicked: this.formSavedClicked,
        cancelClicked: this.cancelClicked,
        refresh: true,
      })
      // more code..multiple if else block like above
    }  
   }

Answer 1

While this may seem somewhat tedious, it is good to unit test everything that you can.

I would unit test this for a few reasons:

1. You can test edge cases. For example, what do you do if mode is null or is a value you haven't planned for. You need to be able to handle that.
2. For future developers. If someone comes along and changes one of these value accidentally, your tests will fail and you will know something is wrong. This will make it required to change the test if they change the value. Thus verifying the change was actually supposed to occur.

If it can be tested, it should be tested.

Answer 2

As Shashank Vivek has indicated, there seems to be a lot of redundancy. Maybe some common functionality can be factored out.

Apart from that, the code should certainly be tested, but it does not necessarily have to be done with unit-testing. Possibly integration testing or UI testing are better suited approaches: With unit-testing, as you observe correctly, your tests are likely to just duplicate the code. But, they will probably not be very valuable in the sense that they will not help you to find bugs.

I assume that these settings are meant to configure the behaviour of some widget library or something similar. Certainly you can write a test that checks that for mode "edit" the value for refresh is false . This test is based on your assumption that this setting will lead to a certain behaviour of that respective widget. But, even if your assumption is wrong, the unit-test will still pass because it simply reflects your own wrong understanding.

To see if these settings are correct, you therefore will have to perform tests where your code is integrated with the widget library, to see that the setup actually leads to the expected effect - but this is then no longer unit-testing.