/** * building keys. */ @Test public void keys() { Set<String> keys0 = ValueOptionMap.keys(); assertThat(keys0, hasSize(0)); // ordered Set<String> keys1 = ValueOptionMap.keys("a"); assertThat(keys1, contains("a")); Set<String> keysN = ValueOptionMap.keys("a", "b", "c", "d", "e"); assertThat(keysN, contains("a", "b", "c", "d", "e")); // ordered }