Detect error messages in response output

[mstrelan]

Before:

Testing /data/app/modules/custom/snsw_news/tests/src/Functional

Behat\Mink\Exception\ElementNotFoundException : Element matching css "article .tile-grid a:first-child" not found.

After:

Testing /data/app/modules/custom/snsw_news/tests/src/Functional

ErrorException : The website encountered an unexpected error. Please try again later.

Error: Call to undefined method Drupal\Core\Field\FieldItemList::viewzzz() in Drupal\snsw_profile\Entity\Node\News->build() (line 187 of profiles/custom/snsw_profile/src/Entity/Node/News.php). Drupal\snsw_profile\Handler\SnswNodeViewBuilder->getBuildDefaults() (Line: 157)

[mstrelan]

Note, this won't detect Fatal Error messages, e.g. OOM. Maybe we could expand this a little.

[mstrelan]

Would be nice if this also covered form submissions and other link clicks. One way to achieve this would be to override the htmlOutput function and detect the error then. The html output contains other messages before the page content so we can't use str_starts_with anymore, and may need to strip some other cruft. Maybe it could check str_contains in the $message and then call $this->getSession()->getPage()->getContent() again to get the error to display.