### Question:
RealValue extends Value { @Override RealValue toRealValue () { return this; } RealValue(double value);   RealValue(String value); @Override String toString();  }### Answer:
@Test public void testToRealValue () { assertEquals ("-1,23", mNegativeValue.toRealValue ().toString ()); assertEquals ("0", mZeroValue.toRealValue ().toString ()); assertEquals ("1,23", mPositiveValue.toRealValue ().toString ()); }