@Test
    void anyMatch() {
        assertTrue(instance.anyMatch(ELEMENT::equals));
        assertFalse(SingletonStream.of(OTHER_ELEMENT).anyMatch(ELEMENT::equals));

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