@Test public void unionInto() { MutableSet<String> set = MultiReaderUnifiedSet.newSetWith("1", "2", "3", "4").asReadUntouchable(); MutableSet<String> union = set.unionInto(UnifiedSet.newSetWith("a", "b", "c", "1"), UnifiedSet.<String>newSet()); Verify.assertSize(set.size() + 3, union); Assert.assertTrue( union.containsAllIterable(Interval.oneTo(set.size()).transform(Functions.getToString()))); Verify.assertContainsAll(union, "a", "b", "c"); Assert.assertEquals( set, set.unionInto(UnifiedSet.newSetWith("1"), UnifiedSet.<String>newSet())); }