/** * @test * @return void * @covers \Magento\Theme\Model\Design\Backend\Theme::beforeSave * @covers \Magento\Theme\Model\Design\Backend\Theme::__construct */ public function testBeforeSave() { $this->design->expects($this->once())->method('setDesignTheme')->with('some_value', Area::AREA_FRONTEND); $this->model->setValue('some_value'); $this->assertInstanceOf(get_class($this->model), $this->model->beforeSave()); }