public function testGetBlockHtml()
{
// Without layout
/** @var $blockFactory \Magento\Framework\View\Element\BlockFactory */
$blockFactory = \Magento\TestFramework\Helper\Bootstrap::getObjectManager()->get('Magento\\Framework\\View\\Element\\BlockFactory');
$block1 = $blockFactory->createBlock('Magento\\Framework\\View\\Element\\Text');
$block1->setText('Block text');
$block1->setNameInLayout('block');
$html = $this->_block->getBlockHtml('block');
$this->assertInternalType('string', $html);
$this->assertEmpty($html);
// With layout
$expected = 'Block2';
$block2 = $this->_createBlockWithLayout('block2', 'block2', 'Magento\\Framework\\View\\Element\\Text');
$block3 = $this->_createBlockWithLayout('block3', 'block3');
$block2->setText($expected);
$html = $block3->getBlockHtml('block2');
$this->assertInternalType('string', $html);
$this->assertEquals($expected, $html);
}