@Test
public void testExec() {

    NodeValue v1 = NodeValue.makeNode("<http://www.opengis.net/def/crs/EPSG/0/27700> Polygon((30 40, 30 70, 90 70, 90 40, 30 40))", WKTDatatype.INSTANCE);
    NodeValue v2 = NodeValue.makeNode("<http://www.opengis.net/def/crs/EPSG/0/27700> Polygon((80 15, 80 45, 140 45, 140 15, 80 15))", WKTDatatype.INSTANCE);
    SymmetricDifferenceFF instance = new SymmetricDifferenceFF();
    NodeValue expResult = NodeValue.makeNode("<http://www.opengis.net/def/crs/EPSG/0/27700> MULTIPOLYGON(((30 40, 30 70, 90 70, 90 45, 80 45, 80 40, 30 40)), ((80 40, 90 40, 90 45, 140 45, 140 15, 80 15, 80 40)))", WKTDatatype.INSTANCE);
    NodeValue result = instance.exec(v1, v2);
    assertEquals(expResult, result);
}