SetExpression extends Expression { @Override public String toString() { return getPropertyName() + " " + getOperator() + " [" + Joiner.on(',').join(values) + "]"; } SetExpression(Operator operator, String propertyName,
            final Object[] values); Object[] getValues(); @Override String toString(); @Override int hashCode(); @Override boolean equals(Object obj);  }
@Test public void testToString() { String expected = propertyName + " " + operator + " [" + Joiner.on(',').join(testValues) + "]"; assertEquals(expected, e.toString()); }