Index: tests/phpunit/tests/user.php
===================================================================
--- tests/phpunit/tests/user.php	(revision 27224)
+++ tests/phpunit/tests/user.php	(working copy)
@@ -627,4 +627,18 @@
 		// If this test fails, it will error out for calling the to_array() method on a non-object.
 		$this->assertInstanceOf( 'WP_Error', wp_update_user( array( 'ID' => $user_id ) ) );
 	}
+
+	/**
+	 * @ticket 24618
+	 */
+	function test_validate_username() {
+
+		$this->assertTrue( validate_username( 'testusername' ) );
+		$this->assertTrue( validate_username( 'JohnDoe' ) );
+		$this->assertTrue( validate_username( 'test@test.com' ) );
+		$this->assertFalse( validate_username( '' ) );
+		$this->assertFalse( validate_username( '@#&99sd' ) );
+
+	}
+	
 }