@Test
    void peek() {
        final AtomicInteger cnt = new AtomicInteger();
        instance.peek(unused -> cnt.getAndIncrement()).forEach(blackHole());
        assertEquals(1, cnt.get());
    }
Test of mapToInt method, of class SingletonStream.
common-parent/singletonstream/src/test/java/com/speedment/common/singletonstream/SingletonStreamTest.java