feat(mat-select): Improve mat-select harness DX

[behzadmehrabi]

Feature Description

Currently, when using matSelectHarness.getOptions(), an empty array is returned if the matSelectHarness.open() method is not called beforehand. This can be confusing for users, who may not realize they need to call matSelectHarness.open() first.

To improve the user experience, I suggest adding an error message similar to what is done in matAutoCompleteHarness, so that if getOptions() is called before open(), an error will be thrown informing the user to call open() first.

This change would save users time and frustration by providing immediate feedback on what they need to do to correctly use the getOptions() method.

matAutoComplete implementation:

components/src/material/autocomplete/testing/autocomplete-harness.ts

Line 80 in 22e928c

if (!(await this.isOpen())) {

I can make a PR for it :)

Thanks.

[yogeshgadge]

I have the same issue and dealing with this work around but should not need to.

export class SelectHarness extends MatSelectHarness {
async getOptions(
    filter?: Omit<OptionHarnessFilters, 'ancestor'>,
    openIfRequired = false
  ): Promise<MatOptionHarness[]> {
    const isOpen = await this.isOpen();
    let closeMe = false;
    if (openIfRequired && !isOpen) {
      closeMe = true;
      await this.open();
      await this.isOpen();
    }
    const optionsH = await super.getOptions(filter);
    console.log('options', optionsH.length);

    if (openIfRequired && closeMe) {
      await this.close();
    }
    return optionsH;
  }
}

Then use it like select.getOptions({}, true); passing true at the end.