@Test
public void testExec() {

    NodeValue v1 = NodeValue.makeNode("<http://www.opengis.net/def/crs/EPSG/0/4326> POINT(10.0 20.0)", WKTDatatype.INSTANCE);
    NodeValue v2 = NodeValue.makeNode("<http://www.opengis.net/def/crs/EPSG/0/4326> POINT(10.0 21.0)", WKTDatatype.INSTANCE);
    NodeValue v3 = NodeValue.makeNode(NodeFactory.createURI(Unit_URI.KILOMETER_URL));
    DistanceFF instance = new DistanceFF();
    double expResult = 109.5057;
    double result = instance.exec(v1, v2, v3).getDouble();
    assertEquals(expResult, result, 0.0001);
}