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