Extract page content while simple testing with xpath and DOM

It is sometimes useful to grab content from the page that is currently tested. The idea is to search for the tag with xpath then convert it to DOM to get data... For instance, let's get the title and the href value of the second tab.

$tab = $this->xpath("//ul[contains(@class, 'tabs--primary')]/li[2]/a");
$link_title = dom_import_simplexml($tab[0])->nodeValue; // Edit
$href =  dom_import_simplexml($tab[0])->getAttribute('href'); // node/xx/edit
 
//note that $tab[0])->getAttribute("src"); seems to work as well
// or easier to get the href $this->xpath("//ul[contains(@class, 'tabs--primary')]/li[2]/a/@href");

Display errors - WSOD

The bootstrap override the values you could set to display error ad the reporting level. To be 100% sure everything is printed out when something fails in a blank screen (wsod), make index.php like this:

Properly render a field

Drupal offers a few (sometimes complicated...) solutions to output a field. Lets take an example with a date field.
To display the full rendered field: field_view_field()