@Test
    public void testFindMissing() {
        TopicPartition foo0 = new TopicPartition("foo", 0);
        TopicPartition foo1 = new TopicPartition("foo", 1);
        TopicPartition bar0 = new TopicPartition("bar", 0);
        TopicPartition bar1 = new TopicPartition("bar", 1);
        TopicPartition baz0 = new TopicPartition("baz", 0);
        TopicPartition baz1 = new TopicPartition("baz", 1);
        assertEquals(toSet(), FetchSessionHandler.findMissing(toSet(foo0), toSet(foo0)));
        assertEquals(toSet(foo0), FetchSessionHandler.findMissing(toSet(foo0), toSet(foo1)));
        assertEquals(toSet(foo0, foo1),
            FetchSessionHandler.findMissing(toSet(foo0, foo1), toSet(baz0)));
        assertEquals(toSet(bar1, foo0, foo1),
            FetchSessionHandler.findMissing(toSet(foo0, foo1, bar0, bar1),
                toSet(bar0, baz0, baz1)));
        assertEquals(toSet(),
            FetchSessionHandler.findMissing(toSet(foo0, foo1, bar0, bar1, baz1),
                toSet(foo0, foo1, bar0, bar1, baz0, baz1)));
    }
Create a set of TopicPartitions.  We use a TreeSet, in order to get a deterministic
ordering for test purposes.
clients/src/test/java/org/apache/kafka/clients/FetchSessionHandlerTest.java