@Test
    public void testAppendRecords() {
        TestAppender appender = new TestAppender();
        assertEquals(5, QuorumController.appendRecords(log,
            ControllerResult.of(Arrays.asList(rec(0), rec(1), rec(2), rec(3), rec(4)), null),
            2,
            appender));
    }
Test that certain controller operations finish immediately without putting an event
on the controller queue, if there is nothing to do.
metadata/src/test/java/org/apache/kafka/controller/QuorumControllerTest.java