/**
     * @return void
     */
    public function testExecute()
    {
        $content = ['export'];

        $this->abstractBlockMock
            ->expects($this->once())
            ->method('getExcelFile')
            ->willReturn($content);

        $this->layoutMock
            ->expects($this->once())
            ->method('getChildBlock')
            ->with('adminhtml.block.report.product.lowstock.grid', 'grid.export')
            ->willReturn($this->abstractBlockMock);

        $this->fileFactoryMock
            ->expects($this->once())
            ->method('create')
            ->with('products_lowstock.xml', $content, \Magento\Framework\App\Filesystem\DirectoryList::VAR_DIR);

        $this->exportLowstockExcel->executeInternal();
    }