@Test
    void iteratorOutOfRange() {
        final Iterator<String> iterator = instance.iterator();
        String element = iterator.next();
        assertThrows(NoSuchElementException.class, iterator::next);
    }
Test of mapToInt method, of class SingletonStream.
common-parent/singletonstream/src/test/java/com/speedment/common/singletonstream/SingletonStreamTest.java