diff --git a/lib/phpunit/classes/advanced_testcase.php b/lib/phpunit/classes/advanced_testcase.php
index 23fb2633366..e3b32c30d8b 100644
--- a/lib/phpunit/classes/advanced_testcase.php
+++ b/lib/phpunit/classes/advanced_testcase.php
@@ -637,7 +637,7 @@ abstract class advanced_testcase extends base_testcase {
                 }
                 return TEST_EXTERNAL_FILES_HTTPS_URL.$path;
             }
-            return "https://download.moodle.org/unittest/{$path}";
+            return "https://download.moodle.org/unittest{$path}";
         }
 
         if (defined('TEST_EXTERNAL_FILES_HTTP_URL')) {
@@ -646,7 +646,7 @@ abstract class advanced_testcase extends base_testcase {
             }
             return TEST_EXTERNAL_FILES_HTTP_URL.$path;
         }
-        return "http://download.moodle.org/unittest/{$path}";
+        return "http://download.moodle.org/unittest{$path}";
     }
 
     /**
diff --git a/lib/phpunit/tests/advanced_test.php b/lib/phpunit/tests/advanced_test.php
index 837a21bc428..dd6a93764cb 100644
--- a/lib/phpunit/tests/advanced_test.php
+++ b/lib/phpunit/tests/advanced_test.php
@@ -385,6 +385,30 @@ final class advanced_test extends \advanced_testcase {
         $this->assertTrue($DB->record_exists('user', array('username' => 'onemore')));
     }
 
+    /**
+     * Some basic tests for the getExternalTestFileUrl() method.
+     */
+    public function test_external_file_url(): void {
+        $url = self::getExternalTestFileUrl('testfile.txt');
+        // There should only be a // after the protocol.
+        $this->assertCount(2, explode('//', $url));
+
+        if (defined('TEST_EXTERNAL_FILES_HTTP_URL')) {
+            $this->assertStringContainsString(TEST_EXTERNAL_FILES_HTTP_URL, $url);
+        } else {
+            $this->assertStringContainsString('http://download.moodle.org/unittest', $url);
+        }
+
+        $url = self::getExternalTestFileUrl('testfile.txt', true);
+        $this->assertCount(2, explode('//', $url));
+
+        if (defined('TEST_EXTERNAL_FILES_HTTPS_URL')) {
+            $this->assertStringContainsString(TEST_EXTERNAL_FILES_HTTPS_URL, $url);
+        } else {
+            $this->assertStringContainsString('https://download.moodle.org/unittest', $url);
+        }
+    }
+
     public function test_assert_time_current() {
         $this->assertTimeCurrent(time());