@Test
    void spliterator() {
        final AtomicInteger cnt = new AtomicInteger();
        instance.spliterator().forEachRemaining(s -> cnt.incrementAndGet());
        assertEquals(1, cnt.get());

        assertThrows(IllegalStateException.class, () -> instance.spliterator());
    }
Test of mapToInt method, of class SingletonStream.
common-parent/singletonstream/src/test/java/com/speedment/common/singletonstream/SingletonStreamTest.java