### Question:
IntegerSetConverter { @TypeConverter public static String toString(Set<Integer> set) { if (set == null) return null; String string = ""; for (Integer i : set) { string += i; string += "#"; } return string; }  @TypeConverter static Set<Integer> toSet(String string); @TypeConverter static String toString(Set<Integer> set);  }### Answer:
@Test public void testToString() { assertEquals(nullString, IntegerSetConverter.toString(nullSet)); assertEquals(emptyString, IntegerSetConverter.toString(emptySet)); assertEquals(oneElementString + "#", IntegerSetConverter.toString(oneElementSet)); assertEquals(largeStringSorted, IntegerSetConverter.toString(largeSet)); }