'Testing union().'

def test13_union(self):

    for i in xrange(len(self.geometries.topology_geoms)):
        a = OGRGeometry(self.geometries.topology_geoms[i].wkt_a)
        b = OGRGeometry(self.geometries.topology_geoms[i].wkt_b)
        u1 = OGRGeometry(self.geometries.union_geoms[i].wkt)
        u2 = a.union(b)
        self.assertEqual(u1, u2)
        self.assertEqual(u1, (a | b))
        a |= b
        self.assertEqual(u1, a)
