### Question:
Stats { public Set<String> getStatisticTypes() { if (!statTypes.isEmpty()) return statTypes.keySet(); return null; }  void putStatisticType(Stat stat); Stat getStatisticType(String key); Set<String> getStatisticTypes(); Set<String> getStatisticKeys(); LinkedHashMap<String,Double> getStatistics(String group, String scenario, String step); LinkedHashMap<String,Double> getStatistics(String group, String scenario); LinkedHashMap<String,Double> getStatistics(String groupOrKey); Double getStatistic(String name,String group, String scenario, String step); Double getStatistic(String name,String group, String scenario); Double getStatistic(String name,String groupOrKey); void putStatistic(String name, Double value, String group, String scenario, String step); void putStatistic(String name,Double value, String group, String scenario); void putStatistic(String name,Double value,String groupOrKey); void putKey(String group, String scenario, String step); void putKey(String group, String scenario); void putKey(String groupOrKey); void addStatistics(Stats stats); boolean isEmpty(); static String SEP; }### Answer:
@Test public void testGetStatisticTypes() { Stats stats = new Stats(); stats.putStatisticType(Stats.StatType.COUNT.type); assertEquals("cnt",stats.getStatisticTypes().toArray()[0]); }