testKeyHandlingAltShift() {
    const editableField = new FieldConstructor('testField');
    const plugin = new TestPlugin();
    const e = getBrowserEvent();
    /**
     * @suppress {strictMissingProperties} suppression added to enable type
     * checking
     */
    e.altKey = true;
    /**
     * @suppress {strictMissingProperties} suppression added to enable type
     * checking
     */
    e.shiftKey = true;

    const mockPlugin = new LooseMock(plugin);
    mockPlugin.getTrogClassId().$returns('mockPlugin');
    mockPlugin.registerFieldObject(editableField);
    mockPlugin.isEnabled(editableField).$anyTimes().$returns(true);
    if (BrowserFeature.USES_KEYDOWN) {
      mockPlugin.handleKeyDown(e).$returns(false);
    } else {
      mockPlugin.handleKeyPress(e).$returns(false);
    }
    mockPlugin.handleKeyboardShortcut(e, STRING_KEY, true).$returns(false);
    mockPlugin.$replay();

    editableField.registerPlugin(mockPlugin);

    if (BrowserFeature.USES_KEYDOWN) {
      editableField.handleKeyDown_(e);
    } else {
      editableField.handleKeyPress_(e);
    }

    mockPlugin.$verify();
  }
Make sure that handleKeyboardShortcut is called if alt+shift is
pressed.
@suppress {missingProperties} suppression added to enable type checking