testPluginKeyUp() {
    const editableField = new FieldConstructor('testField');
    const plugin = new TestPlugin();
    const e = getBrowserEvent();

    const mockPlugin = new LooseMock(plugin);
    mockPlugin.getTrogClassId().$returns('mockPlugin');
    mockPlugin.registerFieldObject(editableField);
    mockPlugin.isEnabled(editableField).$anyTimes().$returns(true);
    mockPlugin.handleKeyUp(e);
    mockPlugin.$replay();

    editableField.registerPlugin(mockPlugin);

    editableField.handleKeyUp_(e);

    mockPlugin.$verify();
  }
Test that if a plugin registers keyup, it gets called.
     @suppress {missingProperties} suppression added to enable type checking