Tests enabling and saving drag and drop with an empty node title.
public function testEmptyNodeTitle() {
// Create node.
$this
->drupalGet('/node/add/paragraphed_test');
$this
->getSession()
->getPage()
->pressButton('Add text');
// Enable drag and drop.
$this
->submitForm([], 'Drag & drop');
// Complete drag and drop.
$this
->submitForm([], 'Complete drag & drop');
$this
->assertSession()
->fieldExists('field_paragraphs[0][subform][field_text][0][value]');
$this
->assertSession()
->pageTextNotContains('Title field is required.');
}