diff --git a/lib/phpunit/classes/advanced_testcase.php b/lib/phpunit/classes/advanced_testcase.php
index 2afb8c30e31e0..a7a33bb7b59a2 100644
--- a/lib/phpunit/classes/advanced_testcase.php
+++ b/lib/phpunit/classes/advanced_testcase.php
@@ -76,6 +76,11 @@ final public function runBare() {
             parent::runBare();
             // set DB reference in case somebody mocked it in test
             $DB = phpunit_util::get_global_backup('DB');
+
+            // Deal with any debugging messages.
+            phpunit_util::display_debugging_messages();
+            phpunit_util::reset_debugging();
+
         } catch (Exception $e) {
             // cleanup after failed expectation
             phpunit_util::reset_all_data();
@@ -234,6 +239,70 @@ public function resetAfterTest($reset = true) {
         $this->resetAfterTest = $reset;
     }
 
+    /**
+     * Return debugging messages from the current test.
+     * @return array
+     */
+    public function getDebuggingMessages() {
+        return phpunit_util::get_debugging_messages();
+    }
+
+    /**
+     * Clear all previous debugging messages in current test.
+     * @return array
+     */
+    public function resetDebugging() {
+        return phpunit_util::reset_debugging();
+    }
+
+    /**
+     * Assert that exactly debugging was just called once.
+     *
+     * Discards the debugging message if successful.
+     *
+     * @param null|string $debugmessage null means any
+     * @param null|string $debuglevel null means any
+     * @param string $message
+     */
+    public function assertDebuggingCalled($debugmessage = null, $debuglevel = null, $message = '') {
+        $debugging = phpunit_util::get_debugging_messages();
+        $count = count($debugging);
+
+        if ($count == 0) {
+            if ($message === '') {
+                $message = 'Expectation failed, debugging() not triggered.';
+            }
+            $this->fail($message);
+        }
+        if ($count > 1) {
+            if ($message === '') {
+                $message = 'Expectation failed, debugging() triggered '.$count.' times.';
+            }
+            $this->fail($message);
+        }
+        $this->assertEquals(1, $count);
+
+        $debug = reset($debugging);
+        if ($debugmessage !== null) {
+            $this->assertSame($debugmessage, $debug->message, $message);
+        }
+        if ($debuglevel !== null) {
+            $this->assertSame($debuglevel, $debug->level, $message);
+        }
+
+        phpunit_util::reset_debugging();
+    }
+
+    public function assertDebuggingNotCalled($message = '') {
+        $debugging = phpunit_util::get_debugging_messages();
+        $count = count($debugging);
+
+        if ($message === '') {
+            $message = 'Expectation failed, debugging() was triggered.';
+        }
+        $this->assertEquals(0, $count, $message);
+    }
+
     /**
      * Cleanup after all tests are executed.
      *
diff --git a/lib/phpunit/classes/database_driver_testcase.php b/lib/phpunit/classes/database_driver_testcase.php
index dc07596467696..09b7dd2544b11 100644
--- a/lib/phpunit/classes/database_driver_testcase.php
+++ b/lib/phpunit/classes/database_driver_testcase.php
@@ -133,4 +133,68 @@ public static function tearDownAfterClass() {
         phpunit_util::reset_all_data();
         parent::tearDownAfterClass();
     }
+
+    /**
+     * Return debugging messages from the current test.
+     * @return array
+     */
+    public function getDebuggingMessages() {
+        return phpunit_util::get_debugging_messages();
+    }
+
+    /**
+     * Clear all previous debugging messages in current test.
+     * @return array
+     */
+    public function resetDebugging() {
+        return phpunit_util::reset_debugging();
+    }
+
+    /**
+     * Assert that exactly debugging was just called once.
+     *
+     * Discards the debugging message if successful.
+     *
+     * @param null|string $debugmessage null means any
+     * @param null|string $debuglevel null means any
+     * @param string $message
+     */
+    public function assertDebuggingCalled($debugmessage = null, $debuglevel = null, $message = '') {
+        $debugging = phpunit_util::get_debugging_messages();
+        $count = count($debugging);
+
+        if ($count == 0) {
+            if ($message === '') {
+                $message = 'Expectation failed, debugging() not triggered.';
+            }
+            $this->fail($message);
+        }
+        if ($count > 1) {
+            if ($message === '') {
+                $message = 'Expectation failed, debugging() triggered '.$count.' times.';
+            }
+            $this->fail($message);
+        }
+        $this->assertEquals(1, $count);
+
+        $debug = reset($debugging);
+        if ($debugmessage !== null) {
+            $this->assertSame($debugmessage, $debug->message, $message);
+        }
+        if ($debuglevel !== null) {
+            $this->assertSame($debuglevel, $debug->level, $message);
+        }
+
+        phpunit_util::reset_debugging();
+    }
+
+    public function assertDebuggingNotCalled($message = '') {
+        $debugging = phpunit_util::get_debugging_messages();
+        $count = count($debugging);
+
+        if ($message === '') {
+            $message = 'Expectation failed, debugging() was triggered.';
+        }
+        $this->assertEquals(0, $count, $message);
+    }
 }
diff --git a/lib/phpunit/classes/util.php b/lib/phpunit/classes/util.php
index de96f3dbeb94b..d9b0d571aa09e 100644
--- a/lib/phpunit/classes/util.php
+++ b/lib/phpunit/classes/util.php
@@ -57,6 +57,9 @@ class phpunit_util {
     /** @var resource used for prevention of parallel test execution */
     protected static $lockhandle = null;
 
+    /** @var array list of debugging messages triggered during the last test execution */
+    protected static $debuggings = array();
+
     /**
      * Prevent parallel test execution - this can not work in Moodle because we modify database and dataroot.
      *
@@ -544,6 +547,10 @@ public static function reset_dataroot() {
     public static function reset_all_data($logchanges = false) {
         global $DB, $CFG, $USER, $SITE, $COURSE, $PAGE, $OUTPUT, $SESSION, $GROUPLIB_CACHE;
 
+        // Show any unhandled debugging messages, the runbare() could already reset it.
+        self::display_debugging_messages();
+        self::reset_debugging();
+
         // reset global $DB in case somebody mocked it
         $DB = self::get_global_backup('DB');
 
@@ -1160,4 +1167,70 @@ private static function directory_has_tests($dir) {
         }
         return false;
     }
+
+    /**
+     * To be called from debugging() only.
+     * @param string $message
+     * @param int $level
+     * @param string $from
+     */
+    public static function debugging_triggered($message, $level, $from) {
+        // Store only if debugging triggered from actual test,
+        // we need normal debugging outside of tests to find problems in our phpunit integration.
+        $backtrace = debug_backtrace();
+
+        foreach ($backtrace as $bt) {
+            $intest = false;
+            if (isset($bt['object']) and is_object($bt['object'])) {
+                if ($bt['object'] instanceof PHPUnit_Framework_TestCase) {
+                    if (strpos($bt['function'], 'test') === 0) {
+                        $intest = true;
+                        break;
+                    }
+                }
+            }
+        }
+        if (!$intest) {
+            return false;
+        }
+
+        $debug = new stdClass();
+        $debug->message = $message;
+        $debug->level   = $level;
+        $debug->from    = $from;
+
+        self::$debuggings[] = $debug;
+
+        return true;
+    }
+
+    /**
+     * Resets the list of debugging messages.
+     */
+    public static function reset_debugging() {
+        self::$debuggings = array();
+    }
+
+    /**
+     * Returns all debugging messages triggered during test.
+     * @return array with instances having message, level and stacktrace property.
+     */
+    public static function get_debugging_messages() {
+        return self::$debuggings;
+    }
+
+    /**
+     * Prints out any debug messages accumulated during test execution.
+     * @return bool false if no debug messages, true if debug triggered
+     */
+    public static function display_debugging_messages() {
+        if (empty(self::$debuggings)) {
+            return false;
+        }
+        foreach(self::$debuggings as $debug) {
+            echo 'Debugging: ' . $debug->message . "\n" . trim($debug->from) . "\n";
+        }
+
+        return true;
+    }
 }
diff --git a/lib/phpunit/tests/advanced_test.php b/lib/phpunit/tests/advanced_test.php
index 302ab1f7bb559..4b6e75fc04509 100644
--- a/lib/phpunit/tests/advanced_test.php
+++ b/lib/phpunit/tests/advanced_test.php
@@ -36,6 +36,40 @@
  */
 class core_phpunit_advanced_testcase extends advanced_testcase {
 
+    public function test_debugging() {
+        global $CFG;
+        $this->resetAfterTest();
+
+        debugging('hokus');
+        $this->assertDebuggingCalled();
+        debugging('pokus');
+        $this->assertDebuggingCalled('pokus');
+        debugging('pokus', DEBUG_MINIMAL);
+        $this->assertDebuggingCalled('pokus', DEBUG_MINIMAL);
+        $this->assertDebuggingNotCalled();
+
+        debugging('a');
+        debugging('b', DEBUG_MINIMAL);
+        debugging('c', DEBUG_DEVELOPER);
+        $debuggings = $this->getDebuggingMessages();
+        $this->assertEquals(3, count($debuggings));
+        $this->assertSame('a', $debuggings[0]->message);
+        $this->assertSame(DEBUG_NORMAL, $debuggings[0]->level);
+        $this->assertSame('b', $debuggings[1]->message);
+        $this->assertSame(DEBUG_MINIMAL, $debuggings[1]->level);
+        $this->assertSame('c', $debuggings[2]->message);
+        $this->assertSame(DEBUG_DEVELOPER, $debuggings[2]->level);
+
+        $this->resetDebugging();
+        $this->assertDebuggingNotCalled();
+        $debuggings = $this->getDebuggingMessages();
+        $this->assertEquals(0, count($debuggings));
+
+        $CFG->debug = DEBUG_NONE;
+        debugging('hokus');
+        $this->assertDebuggingNotCalled();
+    }
+
     public function test_set_user() {
         global $USER, $DB;
 
diff --git a/lib/weblib.php b/lib/weblib.php
index d18546206a1db..3c0dc19e982b2 100644
--- a/lib/weblib.php
+++ b/lib/weblib.php
@@ -2853,9 +2853,13 @@ function debugging($message = '', $level = DEBUG_NORMAL, $backtrace = null) {
         }
         $from = format_backtrace($backtrace, CLI_SCRIPT);
         if (PHPUNIT_TEST) {
-            echo 'Debugging: ' . $message . "\n" . $from;
+            if (phpunit_util::debugging_triggered($message, $level, $from)) {
+                // We are inside test, the debug message was logged.
+                return true;
+            }
+        }
 
-        } else if (NO_DEBUG_DISPLAY) {
+        if (NO_DEBUG_DISPLAY) {
             // script does not want any errors or debugging in output,
             // we send the info to error log instead
             error_log('Debugging: ' . $message . $from);