@Test
public void evaluateFieldRef(){

	FieldName name = new FieldName("x");
	FieldRef expression = new FieldRef(name);
	assertEquals("3", evaluate(expression, createContext(name, "3")));
	assertEquals(null, evaluate(expression, createContext(name, null)));
	expression.setMapMissingTo("Missing");
	assertEquals("Missing", evaluate(expression, createContext(name, null)));
}