И что валидатору не нравитьтся... уже мозг сломал, тест проходит В методе testHashMapStorage должно быть выполнено сравнение времени получения множества ключей и множества значений для стратегий HashMapStorageStrategy и HashBiMapStorageStrategy.
Set<Long> ids = new HashSet<>();
Assert.assertTrue(timeWhithHashMapIds > timeWhithHashBiMapIds);
Assert.assertNotEquals(timeWhithHashMapStrings, timeWhithHashBiMapStrings,30);
public class SpeedTest extends Assert {
    public long getTimeForGettingIds(Shortener shortener, Set<String> strings, Set<Long> ids) {

        Long startTime = System.nanoTime()/ 1000;
        strings.forEach(str -> ids.add(shortener.getId(str)));
        Long endTime = System.nanoTime()/ 1000;
        return endTime - startTime;
    }

    public long getTimeForGettingStrings(Shortener shortener, Set<Long> ids, Set<String> strings) {
        Long startTime = System.nanoTime()/ 1000;
        ids.forEach(id -> strings.add(shortener.getString(id)));
        Long endTime = System.nanoTime()/ 1000;
        return endTime - startTime;
    }

    @Test
    public void testHashMapStorage() {
        Shortener shortener1 = new Shortener(new HashMapStorageStrategy());
        Shortener shortener2 = new Shortener(new HashBiMapStorageStrategy());
        Set<String> origStrings = new HashSet<>();
        for (int i = 0; i < 10000; i++) {
            origStrings.add(Helper.generateRandomString());
        }
        Set<Long> ids = new HashSet<>();
        Long timeWhithHashMapIds= getTimeForGettingIds(shortener1, origStrings, ids);
        Long timeWhithHashMapStrings = getTimeForGettingStrings(shortener1,ids,new HashSet<String>());

        Set<Long> idsBi = new HashSet<>();
        Long timeWhithHashBiMapIds = getTimeForGettingIds(shortener2, origStrings,idsBi);
        Long timeWhithHashBiMapStrings = getTimeForGettingStrings(shortener1,idsBi,new HashSet<String>());


        Assert.assertTrue(timeWhithHashMapIds > timeWhithHashBiMapIds);
        Assert.assertNotEquals(timeWhithHashMapStrings, timeWhithHashBiMapStrings,30);
    }
}