ence';
              assert_equals(sourceBuffer.mode, 'sequence', 'mode after setting it to \'sequence\'');

              // Setting a mode that is not in AppendMode IDL enum should be ignored and not cause exception.
              sourceBuffer.mode = 'invalidmode';
              sourceBuffer.mode = null;
              sourceBuffer.mode = '';
              sourceBuffer.mode = 'Segments';
              assert_equals(sourceBuffer.mode, 'sequence', 'mode unchanged by attempts to set invalid modes');

        