### Question:
TimeSum { public void add(int hoursToAdd, int minutesToAdd) { if (hoursToAdd < 0 || minutesToAdd < 0) { throw new IllegalArgumentException("both values have to be >= 0"); } hours += hoursToAdd; minutes += minutesToAdd; balance(); }  void set(int hours, int minutes); void add(int hoursToAdd, int minutesToAdd); void substract(int hoursToSubstract, int minutesToSubstract); void addOrSubstract(TimeSum timeSum); @Override String toString(); int getAsMinutes(); void reset();  }### Answer:
@Test public void add() { add(0, 75); assertTime("1:15"); add(2, 65); assertTime("4:20"); }