diff --git a/lib/behat/lib.php b/lib/behat/lib.php
index 559821ee5b2..73745500bee 100644
--- a/lib/behat/lib.php
+++ b/lib/behat/lib.php
@@ -134,7 +134,7 @@ function behat_error_handler($errno, $errstr, $errfile, $errline, $errcontext) {
     }
 
     // Wrapping the output.
-    echo '<div class="phpdebugmessage">' . PHP_EOL;
+    echo '<div class="phpdebugmessage" data-rel="phpdebugmessage">' . PHP_EOL;
     echo "$errnostr: $errstr in $errfile on line $errline" . PHP_EOL;
     echo '</div>';
 
diff --git a/lib/outputrenderers.php b/lib/outputrenderers.php
index 3c90a272ed8..401778318aa 100644
--- a/lib/outputrenderers.php
+++ b/lib/outputrenderers.php
@@ -2405,7 +2405,7 @@ EOD;
             $message .= '<p class="errormessage">' . get_string('installproblem', 'error') . '</p>';
             //It is usually not possible to recover from errors triggered during installation, you may need to create a new database or use a different database prefix for new installation.
         }
-        $output .= $this->box($message, 'errorbox');
+        $output .= $this->box($message, 'errorbox', array('data-rel' => 'fatalerror'));
 
         if (debugging('', DEBUG_DEVELOPER)) {
             if (!empty($debuginfo)) {
@@ -2552,10 +2552,11 @@ EOD;
      * @param string $contents The contents of the box
      * @param string $classes A space-separated list of CSS classes
      * @param string $id An optional ID
+     * @param array $attributes An array of other attributes to give the box.
      * @return string the HTML to output.
      */
-    public function box($contents, $classes = 'generalbox', $id = null) {
-        return $this->box_start($classes, $id) . $contents . $this->box_end();
+    public function box($contents, $classes = 'generalbox', $id = null, $attributes = array()) {
+        return $this->box_start($classes, $id, $attributes) . $contents . $this->box_end();
     }
 
     /**
@@ -2563,12 +2564,14 @@ EOD;
      *
      * @param string $classes A space-separated list of CSS classes
      * @param string $id An optional ID
+     * @param array $attributes An array of other attributes to give the box.
      * @return string the HTML to output.
      */
-    public function box_start($classes = 'generalbox', $id = null) {
+    public function box_start($classes = 'generalbox', $id = null, $attributes = array()) {
         $this->opencontainers->push('box', html_writer::end_tag('div'));
-        return html_writer::start_tag('div', array('id' => $id,
-                'class' => 'box ' . renderer_base::prepare_classes($classes)));
+        $attributes['id'] = $id;
+        $attributes['class'] = 'box ' . renderer_base::prepare_classes($classes);
+        return html_writer::start_tag('div', $attributes);
     }
 
     /**
diff --git a/lib/setuplib.php b/lib/setuplib.php
index e08d3c4ffd8..b44e80b51ae 100644
--- a/lib/setuplib.php
+++ b/lib/setuplib.php
@@ -665,7 +665,7 @@ function format_backtrace($callers, $plaintext = false) {
         return '';
     }
 
-    $from = $plaintext ? '' : '<ul style="text-align: left">';
+    $from = $plaintext ? '' : '<ul style="text-align: left" data-rel="backtrace">';
     foreach ($callers as $caller) {
         if (!isset($caller['line'])) {
             $caller['line'] = '?'; // probably call_user_func()
diff --git a/lib/tests/behat/behat_hooks.php b/lib/tests/behat/behat_hooks.php
index 6c5efe43029..f487c8f7da5 100644
--- a/lib/tests/behat/behat_hooks.php
+++ b/lib/tests/behat/behat_hooks.php
@@ -244,14 +244,13 @@ class behat_hooks extends behat_base {
         try {
 
             // Exceptions.
-            $exceptionsxpath = "//*[contains(concat(' ', normalize-space(@class), ' '), ' errorbox ')]" .
-                "/descendant::p[contains(concat(' ', normalize-space(@class), ' '), ' errormessage ')]";
+            $exceptionsxpath = "//div[@data-rel='fatalerror']";
             // Debugging messages.
-            $debuggingxpath = "//*[contains(concat(' ', normalize-space(@class), ' '), ' debuggingmessage ')]";
+            $debuggingxpath = "//div[@data-rel='debugging']";
             // PHP debug messages.
-            $phperrorxpath = "//*[contains(concat(' ', normalize-space(@class), ' '), ' phpdebugmessage ')]";
+            $phperrorxpath = "//div[@data-rel='phpdebugmessage']";
             // Any other backtrace.
-            $othersxpath = "(//*[contains(., ': call to ')])[1]";
+            $othersxpath = "//ul[@data-rel='backtrace']";
 
             $xpaths = array($exceptionsxpath, $debuggingxpath, $phperrorxpath, $othersxpath);
             $joinedxpath = implode(' | ', $xpaths);
diff --git a/lib/weblib.php b/lib/weblib.php
index 24f5a935ff7..c9b617574f1 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -2820,7 +2820,7 @@ function debugging($message = '', $level = DEBUG_NORMAL, $backtrace = null) {
             if (CLI_SCRIPT) {
                 echo "++ $message ++\n$from";
             } else {
-                echo '<div class="notifytiny debuggingmessage">' . $message . $from . '</div>';
+                echo '<div class="notifytiny debuggingmessage" data-rel="debugging">' , $message , $from , '</div>';
             }
 
         } else {