### Question:
IntegerValue extends Value { @Override IntegerValue toIntegerValue () { return this; } IntegerValue(int value);   IntegerValue(String value); @Override String toString();  }### Answer:
@Test public void testToIntegerValue () { assertEquals ("-123", mNegativeValue.toIntegerValue ().toString ()); assertEquals ("0", mZeroValue.toIntegerValue ().toString ()); assertEquals ("123", mPositiveValue.toIntegerValue ().toString ()); }