Feature Description

I would like to see a method on TestElement that allows for setting properties on the underlying element. Specifically, for setting the files property on an input element.

Use Case

I am creating a feature for an app to allow users to change their profile picture (avatar). This feature is similar to the one on Google Accounts (shown below).

I ran into a problem trying to create a ComponentHarness that would allow me to simulate the change event on the underlying input element with a list of files. The files need to be set on the underlying input element before dispatching a change event. There is currently no way to set properties on the underlying element before dispatching the event. Currently since I am only using the ComponentHarness for unit tests I simple cast the TestElement.

  async setFiles(files: File[]) {
    const input = await this._input();

    if (files && input instanceof UnitTestElement) {
      Object.defineProperty((input as UnitTestElement).element, 'files', {
        configurable: true,
        enumerable: true,
        writable: true,
        value: files,
      });
    }

    input.dispatchEvent('change');
  }

The other way to do this, AFAIK is to extend TestElement and TestBedHarnessEnvironment to return the extended TestElement.

I am not sure if creating a generic setProperties method on TestElement similar to being able to set EventData on events is the way to go or if a specific setInputFiles similar to setInputValue should be added.