### Question:
ExerciseKey { @Override public String toString() { return courseName + "/" + exerciseName; } ExerciseKey(String courseName, String exerciseName); String getCourseName(); String getExerciseName(); @Override boolean equals(Object obj); @Override int hashCode(); @Override String toString();  }### Answer:
@Test public void toStringReturnCorrectString() { assertEquals("a/b", ek.toString()); }