MDL-40852 behat: Wrong URLs detection

lib/tests/behat/behat_hooks.php

@@ -59,6 +59,11 @@ class behat_hooks extends behat_base {
      */
     protected static $lastbrowsersessionstart = 0;
 
+    /**
+     * @var For actions that should only run once.
+     */
+    protected static $initprocessesfinished = false;
+
     /**
      * Gives access to moodle codebase, ensures all is ready and sets up the test lock.
      *
@@ -161,6 +166,15 @@ class behat_hooks extends behat_base {
         // Start always in the the homepage.
         $this->getSession()->visit($this->locate_path('/'));
 
+        // Checking that the root path is a Moodle test site.
+        if (self::is_first_scenario()) {
+            $notestsiteexception = new Exception('The base URL (' . $CFG->wwwroot . ') is not a behat test site, ' .
+                'ensure you started the built-in web server in the correct directory');
+            $this->find("xpath", "//head/child::title[normalize-space(.)='Acceptance test site']", $notestsiteexception);
+
+            self::$initprocessesfinished = true;
+        }
+
         // Closing JS dialogs if present. Otherwise they would block this scenario execution.
         if ($this->running_javascript()) {
             try {
@@ -335,4 +349,12 @@ class behat_hooks extends behat_base {
         return preg_replace("/(\n)+/s", "\n", $notags);
     }
 
+    /**
+     * Returns whether the first scenario of the suite is running
+     *
+     * @return bool
+     */
+    protected static function is_first_scenario() {
+        return !(self::$initprocessesfinished);
+    }
 }