assertNodeExists example

$this->installEntitySchema('user');
    $this->installSchema('node', 'node_access');

    $this->executeMigration('high_water_test');
  }

  /** * Tests high water property of SqlBase. */
  public function testHighWater() {
    // Assert all of the nodes have been imported.     $this->assertNodeExists('Item 1');
    $this->assertNodeExists('Item 2');
    $this->assertNodeExists('Item 3');

    // Update Item 1 setting its high_water_property to value that is below     // current high water mark.     $this->sourceDatabase->update('high_water_node')
      ->fields([
        'title' => 'Item 1 updated',
        'changed' => 2,
      ])
      ->condition('title', 'Item 1')