@Test public void cartesianProduct() { MutableSet<String> set = MultiReaderUnifiedSet.newSetWith("1", "2", "3", "4").asReadUntouchable(); LazyIterable<Pair<String, String>> cartesianProduct = set.cartesianProduct(UnifiedSet.newSetWith("One", "Two")); Verify.assertIterableSize(set.size() * 2, cartesianProduct); Assert.assertEquals( set, cartesianProduct .filter(Predicates.attributeEqual(Functions.<String>secondOfPair(), "One")) .transform(Functions.<String>firstOfPair()) .toSet()); }