IDFunctionExpression extends FunctionExpressionImpl { public Object evaluate(Object obj) { if (obj instanceof Attribute) { Attribute att = (Attribute) obj; return att.getIdentifier(); } return null; } IDFunctionExpression(); Object evaluate(Object obj);  }
@Test public void testGetValue() throws Exception { Object fid = feature.getIdentifier(); Object found = idExpr.evaluate(feature); assertNotNull(found); assertEquals(fid, found); }