void () { MostlySingularMultiMap<String, String> mapEmpty = new MostlySingularMultiMap<>(); MostlySingularMultiMap<String, String> mapWithOne = new MostlySingularMultiMap<>(); MostlySingularMultiMap<String, String> mapWithMultiple = new MostlySingularMultiMap<>(); mapWithOne.add("1", "a"); mapWithMultiple.add("1", "a"); mapWithMultiple.add("1", "b"); MostlySingularMultiMap<String, String> from = new MostlySingularMultiMap<>(); from.add("1", "x"); from.add("1", "y"); mapEmpty.addAll(from); mapWithOne.addAll(from); mapWithMultiple.addAll(from); mapEmpty.add("1", "mapEmpty"); mapWithOne.add("1", "mapWithOne"); mapWithMultiple.add("1", "mapWithMultiple"); from.add("1", "from"); assertEquals(Arrays.asList("x", "y", "mapEmpty"), ContainerUtil.newArrayList(mapEmpty.get("1"))); assertEquals(Arrays.asList("a", "x", "y", "mapWithOne"), ContainerUtil.newArrayList(mapWithOne.get("1"))); assertEquals(Arrays.asList("a", "b", "x", "y", "mapWithMultiple"), ContainerUtil.newArrayList(mapWithMultiple.get("1"))); assertEquals(Arrays.asList("x", "y", "from"), ContainerUtil.newArrayList(from.get("1"))); }