test_geos.py

import random, unittest, sys
from ctypes import ArgumentError
from django.contrib.gis.geos import \
    GEOSException, GEOSIndexError, \
    GEOSGeometry, Point, LineString, LinearRing, Polygon, \
    MultiPoint, MultiLineString, MultiPolygon, GeometryCollection, \
    fromstr, geos_version, HAS_NUMPY
from django.contrib.gis.geos.base import HAS_GDAL
from django.contrib.gis.tests.geometries import *
    
if HAS_NUMPY: from numpy import array
if HAS_GDAL: from django.contrib.gis.gdal import OGRGeometry, SpatialReference

class GEOSTest(unittest.TestCase):

    def test01a_wkt(self):
        "Testing WKT output."
        for g in wkt_out:
            geom = fromstr(g.wkt)
            self.assertEqual(g.ewkt, geom.wkt)

    def test01b_hex(self):
        "Testing HEX output."
        for g in hex_wkt:
            geom = fromstr(g.wkt)
            self.assertEqual(g.hex, geom.hex)

    def test01c_kml(self):
        "Testing KML output."
        for tg in wkt_out:
            geom = fromstr(tg.wkt)
            kml = getattr(tg, 'kml', False)
            if kml: self.assertEqual(kml, geom.kml)

    def test01d_errors(self):
        "Testing the Error handlers."
        # string-based
        print "\nBEGIN - expecting GEOS_ERROR; safe to ignore.\n"
        for err in errors:
            try:
                g = fromstr(err.wkt)
            except (GEOSException, ValueError):
                pass
        print "\nEND - expecting GEOS_ERROR; safe to ignore.\n"
        
        class NotAGeometry(object):
            pass
        
        # Some other object
        self.assertRaises(TypeError, GEOSGeometry, NotAGeometry())
        # None
        self.assertRaises(TypeError, GEOSGeometry, None)
        # Bad WKB
        self.assertRaises(GEOSException, GEOSGeometry, buffer('0'))
                
    def test01e_wkb(self):
        "Testing WKB output."
        from binascii import b2a_hex
        for g in hex_wkt:
            geom = fromstr(g.wkt)
            wkb = geom.wkb
            self.assertEqual(b2a_hex(wkb).upper(), g.hex)

    def test01f_create_hex(self):
        "Testing creation from HEX."
        for g in hex_wkt:
            geom_h = GEOSGeometry(g.hex)
            # we need to do this so decimal places get normalised
            geom_t = fromstr(g.wkt)
            self.assertEqual(geom_t.wkt, geom_h.wkt)

    def test01g_create_wkb(self):
        "Testing creation from WKB."
        from binascii import a2b_hex
        for g in hex_wkt:
            wkb = buffer(a2b_hex(g.hex))
            geom_h = GEOSGeometry(wkb)
            # we need to do this so decimal places get normalised
            geom_t = fromstr(g.wkt)
            self.assertEqual(geom_t.wkt, geom_h.wkt)

    def test01h_ewkt(self):
        "Testing EWKT."
        srid = 32140
        for p in polygons:
            ewkt = 'SRID=%d;%s' % (srid, p.wkt)
            poly = fromstr(ewkt)
            self.assertEqual(srid, poly.srid)
            self.assertEqual(srid, poly.shell.srid)
            self.assertEqual(srid, fromstr(poly.ewkt).srid) # Checking export
    
    def test02a_points(self):
        "Testing Point objects."
        prev = fromstr('POINT(0 0)')
        for p in points:
            # Creating the point from the WKT
            pnt = fromstr(p.wkt)
            self.assertEqual(pnt.geom_type, 'Point')
            self.assertEqual(pnt.geom_typeid, 0)
            self.assertEqual(p.x, pnt.x)
            self.assertEqual(p.y, pnt.y)
            self.assertEqual(True, pnt == fromstr(p.wkt))
            self.assertEqual(False, pnt == prev)

            # Making sure that the point's X, Y components are what we expect
            self.assertAlmostEqual(p.x, pnt.tuple[0], 9)
            self.assertAlmostEqual(p.y, pnt.tuple[1], 9)

            # Testing the third dimension, and getting the tuple arguments
            if hasattr(p, 'z'):
                self.assertEqual(True, pnt.hasz)
                self.assertEqual(p.z, pnt.z)
                self.assertEqual(p.z, pnt.tuple[2], 9)
                tup_args = (p.x, p.y, p.z)
                set_tup1 = (2.71, 3.14, 5.23)
                set_tup2 = (5.23, 2.71, 3.14)
            else:
                self.assertEqual(False, pnt.hasz)
                self.assertEqual(None, pnt.z)
                tup_args = (p.x, p.y)
                set_tup1 = (2.71, 3.14)
                set_tup2 = (3.14, 2.71)

            # Centroid operation on point should be point itself
            self.assertEqual(p.centroid, pnt.centroid.tuple)

            # Now testing the different constructors
            pnt2 = Point(tup_args)  # e.g., Point((1, 2))
            pnt3 = Point(*tup_args) # e.g., Point(1, 2)
            self.assertEqual(True, pnt == pnt2)
            self.assertEqual(True, pnt == pnt3)

            # Now testing setting the x and y
            pnt.y = 3.14
            pnt.x = 2.71
            self.assertEqual(3.14, pnt.y)
            self.assertEqual(2.71, pnt.x)

            # Setting via the tuple/coords property
            pnt.tuple = set_tup1
            self.assertEqual(set_tup1, pnt.tuple)
            pnt.coords = set_tup2
            self.assertEqual(set_tup2, pnt.coords)
            
            prev = pnt # setting the previous geometry

    def test02b_multipoints(self):
        "Testing MultiPoint objects."
        for mp in multipoints:
            mpnt = fromstr(mp.wkt)
            self.assertEqual(mpnt.geom_type, 'MultiPoint')
            self.assertEqual(mpnt.geom_typeid, 4)

            self.assertAlmostEqual(mp.centroid[0], mpnt.centroid.tuple[0], 9)
            self.assertAlmostEqual(mp.centroid[1], mpnt.centroid.tuple[1], 9)

            self.assertRaises(GEOSIndexError, mpnt.__getitem__, len(mpnt))
            self.assertEqual(mp.centroid, mpnt.centroid.tuple)
            self.assertEqual(mp.points, tuple(m.tuple for m in mpnt))
            for p in mpnt:
                self.assertEqual(p.geom_type, 'Point')
                self.assertEqual(p.geom_typeid, 0)
                self.assertEqual(p.empty, False)
                self.assertEqual(p.valid, True)

    def test03a_linestring(self):
        "Testing LineString objects."
        prev = fromstr('POINT(0 0)')
        for l in linestrings:
            ls = fromstr(l.wkt)
            self.assertEqual(ls.geom_type, 'LineString')
            self.assertEqual(ls.geom_typeid, 1)
            self.assertEqual(ls.empty, False)
            self.assertEqual(ls.ring, False)
            if hasattr(l, 'centroid'):
                self.assertEqual(l.centroid, ls.centroid.tuple)
            if hasattr(l, 'tup'):
                self.assertEqual(l.tup, ls.tuple)
                
            self.assertEqual(True, ls == fromstr(l.wkt))
            self.assertEqual(False, ls == prev)
            self.assertRaises(GEOSIndexError, ls.__getitem__, len(ls))
            prev = ls

            # Creating a LineString from a tuple, list, and numpy array
            self.assertEqual(ls, LineString(ls.tuple))  # tuple
            self.assertEqual(ls, LineString(*ls.tuple)) # as individual arguments
            self.assertEqual(ls, LineString([list(tup) for tup in ls.tuple])) # as list
            self.assertEqual(ls.wkt, LineString(*tuple(Point(tup) for tup in ls.tuple)).wkt) # Point individual arguments
            if HAS_NUMPY: self.assertEqual(ls, LineString(array(ls.tuple))) # as numpy array

    def test03b_multilinestring(self):
        "Testing MultiLineString objects."
        prev = fromstr('POINT(0 0)')
        for l in multilinestrings:
            ml = fromstr(l.wkt)
            self.assertEqual(ml.geom_type, 'MultiLineString')
            self.assertEqual(ml.geom_typeid, 5)

            self.assertAlmostEqual(l.centroid[0], ml.centroid.x, 9)
            self.assertAlmostEqual(l.centroid[1], ml.centroid.y, 9)

            self.assertEqual(True, ml == fromstr(l.wkt))
            self.assertEqual(False, ml == prev)
            prev = ml

            for ls in ml:
                self.assertEqual(ls.geom_type, 'LineString')
                self.assertEqual(ls.geom_typeid, 1)
                self.assertEqual(ls.empty, False)

            self.assertRaises(GEOSIndexError, ml.__getitem__, len(ml))
            self.assertEqual(ml.wkt, MultiLineString(*tuple(s.clone() for s in ml)).wkt)
            self.assertEqual(ml, MultiLineString(*tuple(LineString(s.tuple) for s in ml)))

    def test04_linearring(self):
        "Testing LinearRing objects."
        for rr in linearrings:
            lr = fromstr(rr.wkt)
            self.assertEqual(lr.geom_type, 'LinearRing')
            self.assertEqual(lr.geom_typeid, 2)
            self.assertEqual(rr.n_p, len(lr))
            self.assertEqual(True, lr.valid)
            self.assertEqual(False, lr.empty)

            # Creating a LinearRing from a tuple, list, and numpy array
            self.assertEqual(lr, LinearRing(lr.tuple))
            self.assertEqual(lr, LinearRing(*lr.tuple))
            self.assertEqual(lr, LinearRing([list(tup) for tup in lr.tuple]))
            if HAS_NUMPY: self.assertEqual(lr, LinearRing(array(lr.tuple)))
    
    def test05a_polygons(self):
        "Testing Polygon objects."
        prev = fromstr('POINT(0 0)')
        for p in polygons:
            # Creating the Polygon, testing its properties.
            poly = fromstr(p.wkt)
            self.assertEqual(poly.geom_type, 'Polygon')
            self.assertEqual(poly.geom_typeid, 3)
            self.assertEqual(poly.empty, False)
            self.assertEqual(poly.ring, False)
            self.assertEqual(p.n_i, poly.num_interior_rings)
            self.assertEqual(p.n_i + 1, len(poly)) # Testing __len__
            self.assertEqual(p.n_p, poly.num_points)

            # Area & Centroid
            self.assertAlmostEqual(p.area, poly.area, 9)
            self.assertAlmostEqual(p.centroid[0], poly.centroid.tuple[0], 9)
            self.assertAlmostEqual(p.centroid[1], poly.centroid.tuple[1], 9)

            # Testing the geometry equivalence
            self.assertEqual(True, poly == fromstr(p.wkt))
            self.assertEqual(False, poly == prev) # Should not be equal to previous geometry
            self.assertEqual(True, poly != prev)

            # Testing the exterior ring
            ring = poly.exterior_ring
            self.assertEqual(ring.geom_type, 'LinearRing')
            self.assertEqual(ring.geom_typeid, 2)
            if p.ext_ring_cs:
                self.assertEqual(p.ext_ring_cs, ring.tuple)
                self.assertEqual(p.ext_ring_cs, poly[0].tuple) # Testing __getitem__

            # Testing __getitem__ and __setitem__ on invalid indices
            self.assertRaises(GEOSIndexError, poly.__getitem__, len(poly))
            #self.assertRaises(GEOSIndexError, poly.__setitem__, len(poly), False)
            self.assertRaises(GEOSIndexError, poly.__getitem__, -1)

            # Testing __iter__ 
            for r in poly:
                self.assertEqual(r.geom_type, 'LinearRing')
                self.assertEqual(r.geom_typeid, 2)

            # Testing polygon construction.
            self.assertRaises(TypeError, Polygon.__init__, 0, [1, 2, 3])
            self.assertRaises(TypeError, Polygon.__init__, 'foo')
            rings = tuple(r for r in poly)
            self.assertEqual(poly, Polygon(rings[0], rings[1:]))
            self.assertEqual(poly.wkt, Polygon(*tuple(r for r in poly)).wkt)
            self.assertEqual(poly.wkt, Polygon(*tuple(LinearRing(r.tuple) for r in poly)).wkt)

    def test05b_multipolygons(self):
        "Testing MultiPolygon objects."
        print "\nBEGIN - expecting GEOS_NOTICE; safe to ignore.\n"
        prev = fromstr('POINT (0 0)')
        for mp in multipolygons:
            mpoly = fromstr(mp.wkt)
            self.assertEqual(mpoly.geom_type, 'MultiPolygon')
            self.assertEqual(mpoly.geom_typeid, 6)
            self.assertEqual(mp.valid, mpoly.valid)

            if mp.valid:
                self.assertEqual(mp.num_geom, mpoly.num_geom)
                self.assertEqual(mp.n_p, mpoly.num_coords)
                self.assertEqual(mp.num_geom, len(mpoly))
                self.assertRaises(GEOSIndexError, mpoly.__getitem__, len(mpoly))
                for p in mpoly:
                    self.assertEqual(p.geom_type, 'Polygon')
                    self.assertEqual(p.geom_typeid, 3)
                    self.assertEqual(p.valid, True)
                self.assertEqual(mpoly.wkt, MultiPolygon(*tuple(poly.clone() for poly in mpoly)).wkt)

        print "\nEND - expecting GEOS_NOTICE; safe to ignore.\n"  

    def test06a_memory_hijinks(self):
        "Testing Geometry __del__() on rings and polygons."
        #### Memory issues with rings and polygons

        # These tests are needed to ensure sanity with writable geometries.

        # Getting a polygon with interior rings, and pulling out the interior rings
        poly = fromstr(polygons[1].wkt)
        ring1 = poly[0]
        ring2 = poly[1]

        # These deletes should be 'harmless' since they are done on child geometries
        del ring1 
        del ring2
        ring1 = poly[0]
        ring2 = poly[1]

        # Deleting the polygon
        del poly

        # Access to these rings is OK since they are clones.
        s1, s2 = str(ring1), str(ring2)

        # The previous hijinks tests are now moot because only clones are 
        # now used =)

    def test08_coord_seq(self):
        "Testing Coordinate Sequence objects."
        for p in polygons:
            if p.ext_ring_cs:
                # Constructing the polygon and getting the coordinate sequence
                poly = fromstr(p.wkt)
                cs = poly.exterior_ring.coord_seq

                self.assertEqual(p.ext_ring_cs, cs.tuple) # done in the Polygon test too.
                self.assertEqual(len(p.ext_ring_cs), len(cs)) # Making sure __len__ works

                # Checks __getitem__ and __setitem__
                for i in xrange(len(p.ext_ring_cs)):
                    c1 = p.ext_ring_cs[i] # Expected value
                    c2 = cs[i] # Value from coordseq
                    self.assertEqual(c1, c2)

                    # Constructing the test value to set the coordinate sequence with
                    if len(c1) == 2: tset = (5, 23)
                    else: tset = (5, 23, 8)
                    cs[i] = tset
                    
                    # Making sure every set point matches what we expect
                    for j in range(len(tset)):
                        cs[i] = tset
                        self.assertEqual(tset[j], cs[i][j])

    def test09_relate_pattern(self):
        "Testing relate() and relate_pattern()."
        g = fromstr('POINT (0 0)')
        self.assertRaises(GEOSException, g.relate_pattern, 0, 'invalid pattern, yo')
        for i in xrange(len(relate_geoms)):
            g_tup = relate_geoms[i]
            a = fromstr(g_tup[0].wkt)
            b = fromstr(g_tup[1].wkt)
            pat = g_tup[2]
            result = g_tup[3]
            self.assertEqual(result, a.relate_pattern(b, pat))
            self.assertEqual(pat, a.relate(b))

    def test10_intersection(self):
        "Testing intersects() and intersection()."
        for i in xrange(len(topology_geoms)):
            g_tup = topology_geoms[i]
            a = fromstr(g_tup[0].wkt)
            b = fromstr(g_tup[1].wkt)
            i1 = fromstr(intersect_geoms[i].wkt) 
            self.assertEqual(True, a.intersects(b))
            i2 = a.intersection(b)
            self.assertEqual(i1, i2)
            self.assertEqual(i1, a & b) # __and__ is intersection operator
            a &= b # testing __iand__
            self.assertEqual(i1, a)

    def test11_union(self):
        "Testing union()."
        for i in xrange(len(topology_geoms)):
            g_tup = topology_geoms[i]
            a = fromstr(g_tup[0].wkt)
            b = fromstr(g_tup[1].wkt)
            u1 = fromstr(union_geoms[i].wkt)
            u2 = a.union(b)
            self.assertEqual(u1, u2)
            self.assertEqual(u1, a | b) # __or__ is union operator
            a |= b # testing __ior__
            self.assertEqual(u1, a) 

    def test12_difference(self):
        "Testing difference()."
        for i in xrange(len(topology_geoms)):
            g_tup = topology_geoms[i]
            a = fromstr(g_tup[0].wkt)
            b = fromstr(g_tup[1].wkt)
            d1 = fromstr(diff_geoms[i].wkt)
            d2 = a.difference(b)
            self.assertEqual(d1, d2)
            self.assertEqual(d1, a - b) # __sub__ is difference operator
            a -= b # testing __isub__
            self.assertEqual(d1, a)

    def test13_symdifference(self):
        "Testing sym_difference()."
        for i in xrange(len(topology_geoms)):
            g_tup = topology_geoms[i]
            a = fromstr(g_tup[0].wkt)
            b = fromstr(g_tup[1].wkt)
            d1 = fromstr(sdiff_geoms[i].wkt)
            d2 = a.sym_difference(b)
            self.assertEqual(d1, d2)
            self.assertEqual(d1, a ^ b) # __xor__ is symmetric difference operator
            a ^= b # testing __ixor__
            self.assertEqual(d1, a)

    def test14_buffer(self):
        "Testing buffer()."
        for i in xrange(len(buffer_geoms)):
            g_tup = buffer_geoms[i]
            g = fromstr(g_tup[0].wkt)

            # The buffer we expect
            exp_buf = fromstr(g_tup[1].wkt)

            # Can't use a floating-point for the number of quadsegs.
            self.assertRaises(ArgumentError, g.buffer, g_tup[2], float(g_tup[3]))

            # Constructing our buffer
            buf = g.buffer(g_tup[2], g_tup[3])
            self.assertEqual(exp_buf.num_coords, buf.num_coords)
            self.assertEqual(len(exp_buf), len(buf))

            # Now assuring that each point in the buffer is almost equal
            for j in xrange(len(exp_buf)):
                exp_ring = exp_buf[j]
                buf_ring = buf[j]
                self.assertEqual(len(exp_ring), len(buf_ring))
                for k in xrange(len(exp_ring)):
                    # Asserting the X, Y of each point are almost equal (due to floating point imprecision)
                    self.assertAlmostEqual(exp_ring[k][0], buf_ring[k][0], 9)
                    self.assertAlmostEqual(exp_ring[k][1], buf_ring[k][1], 9)

    def test15_srid(self):
        "Testing the SRID property and keyword."
        # Testing SRID keyword on Point
        pnt = Point(5, 23, srid=4326)
        self.assertEqual(4326, pnt.srid)
        pnt.srid = 3084
        self.assertEqual(3084, pnt.srid)
        self.assertRaises(ArgumentError, pnt.set_srid, '4326')

        # Testing SRID keyword on fromstr(), and on Polygon rings.
        poly = fromstr(polygons[1].wkt, srid=4269)
        self.assertEqual(4269, poly.srid)
        for ring in poly: self.assertEqual(4269, ring.srid)
        poly.srid = 4326
        self.assertEqual(4326, poly.shell.srid)

        # Testing SRID keyword on GeometryCollection
        gc = GeometryCollection(Point(5, 23), LineString((0, 0), (1.5, 1.5), (3, 3)), srid=32021)
        self.assertEqual(32021, gc.srid)
        for i in range(len(gc)): self.assertEqual(32021, gc[i].srid)

        # GEOS may get the SRID from HEXEWKB
        # 'POINT(5 23)' at SRID=4326 in hex form -- obtained from PostGIS
        # using `SELECT GeomFromText('POINT (5 23)', 4326);`.
        hex = '0101000020E610000000000000000014400000000000003740'
        p1 = fromstr(hex)
        self.assertEqual(4326, p1.srid)

        # However, when HEX is exported, the SRID information is lost
        # and set to -1.  Essentially, the 'E' of the EWKB is not
        # encoded in HEX by the GEOS C library for some reason.
        p2 = fromstr(p1.hex)
        self.assertEqual(-1, p2.srid)
        p3 = fromstr(p1.hex, srid=-1) # -1 is intended.
        self.assertEqual(-1, p3.srid)

    def test16_mutable_geometries(self):
        "Testing the mutability of Polygons and Geometry Collections."
        ### Testing the mutability of Polygons ###
        for p in polygons:
            poly = fromstr(p.wkt)

            # Should only be able to use __setitem__ with LinearRing geometries.
            self.assertRaises(TypeError, poly.__setitem__, 0, LineString((1, 1), (2, 2)))

            # Constructing the new shell by adding 500 to every point in the old shell.
            shell_tup = poly.shell.tuple
            new_coords = []
            for point in shell_tup: new_coords.append((point[0] + 500., point[1] + 500.))
            new_shell = LinearRing(*tuple(new_coords))

            # Assigning polygon's exterior ring w/the new shell
            poly.exterior_ring = new_shell
            s = str(new_shell) # new shell is still accessible
            self.assertEqual(poly.exterior_ring, new_shell)
            self.assertEqual(poly[0], new_shell)

        ### Testing the mutability of Geometry Collections
        for tg in multipoints:
            mp = fromstr(tg.wkt)
            for i in range(len(mp)):
                # Creating a random point.
                pnt = mp[i]
                new = Point(random.randint(1, 100), random.randint(1, 100))
                # Testing the assignment
                mp[i] = new
                s = str(new) # what was used for the assignment is still accessible
                self.assertEqual(mp[i], new)
                self.assertEqual(mp[i].wkt, new.wkt)
                self.assertNotEqual(pnt, mp[i])

        # MultiPolygons involve much more memory management because each
        # Polygon w/in the collection has its own rings.
        for tg in multipolygons:
            mpoly = fromstr(tg.wkt)
            for i in xrange(len(mpoly)):
                poly = mpoly[i]
                old_poly = mpoly[i]
                # Offsetting the each ring in the polygon by 500.
                for j in xrange(len(poly)):
                    r = poly[j]
                    for k in xrange(len(r)): r[k] = (r[k][0] + 500., r[k][1] + 500.)
                    poly[j] = r
                
                self.assertNotEqual(mpoly[i], poly)
                # Testing the assignment
                mpoly[i] = poly
                s = str(poly) # Still accessible
                self.assertEqual(mpoly[i], poly)
                self.assertNotEqual(mpoly[i], old_poly)

        # Extreme (!!) __setitem__ -- no longer works, have to detect
        # in the first object that __setitem__ is called in the subsequent
        # objects -- maybe mpoly[0, 0, 0] = (3.14, 2.71)?
        #mpoly[0][0][0] = (3.14, 2.71)
        #self.assertEqual((3.14, 2.71), mpoly[0][0][0])
        # Doing it more slowly..
        #self.assertEqual((3.14, 2.71), mpoly[0].shell[0])
        #del mpoly
    
    def test17_threed(self):
        "Testing three-dimensional geometries."
        # Testing a 3D Point
        pnt = Point(2, 3, 8)
        self.assertEqual((2.,3.,8.), pnt.coords)
        self.assertRaises(TypeError, pnt.set_coords, (1.,2.))
        pnt.coords = (1.,2.,3.)
        self.assertEqual((1.,2.,3.), pnt.coords)

        # Testing a 3D LineString
        ls = LineString((2., 3., 8.), (50., 250., -117.))
        self.assertEqual(((2.,3.,8.), (50.,250.,-117.)), ls.tuple)
        self.assertRaises(TypeError, ls.__setitem__, 0, (1.,2.))
        ls[0] = (1.,2.,3.)
        self.assertEqual((1.,2.,3.), ls[0])
            
    def test18_distance(self):
        "Testing the distance() function."
        # Distance to self should be 0. 
        pnt = Point(0, 0)
        self.assertEqual(0.0, pnt.distance(Point(0, 0)))
    
        # Distance should be 1
        self.assertEqual(1.0, pnt.distance(Point(0, 1)))

        # Distance should be ~ sqrt(2)
        self.assertAlmostEqual(1.41421356237, pnt.distance(Point(1, 1)), 11)

        # Distances are from the closest vertex in each geometry --
        #  should be 3 (distance from (2, 2) to (5, 2)).
        ls1 = LineString((0, 0), (1, 1), (2, 2))
        ls2 = LineString((5, 2), (6, 1), (7, 0))
        self.assertEqual(3, ls1.distance(ls2))

    def test19_length(self):
        "Testing the length property."
        # Points have 0 length.
        pnt = Point(0, 0)
        self.assertEqual(0.0, pnt.length)
        
        # Should be ~ sqrt(2)
        ls = LineString((0, 0), (1, 1))
        self.assertAlmostEqual(1.41421356237, ls.length, 11)

        # Should be circumfrence of Polygon
        poly = Polygon(LinearRing((0, 0), (0, 1), (1, 1), (1, 0), (0, 0)))
        self.assertEqual(4.0, poly.length)

        # Should be sum of each element's length in collection.
        mpoly = MultiPolygon(poly.clone(), poly)
        self.assertEqual(8.0, mpoly.length)

    def test20_emptyCollections(self):
        "Testing empty geometries and collections."
        gc1 = GeometryCollection([])
        gc2 = fromstr('GEOMETRYCOLLECTION EMPTY')
        pnt = fromstr('POINT EMPTY')
        ls = fromstr('LINESTRING EMPTY')
        poly = fromstr('POLYGON EMPTY')
        mls = fromstr('MULTILINESTRING EMPTY')
        mpoly1 = fromstr('MULTIPOLYGON EMPTY')
        mpoly2 = MultiPolygon(())

        for g in [gc1, gc2, pnt, ls, poly, mls, mpoly1, mpoly2]:
            self.assertEqual(True, g.empty)

            # Testing len() and num_geom.
            if isinstance(g, Polygon):
                self.assertEqual(1, len(g)) # Has one empty linear ring
                self.assertEqual(1, g.num_geom)
                self.assertEqual(0, len(g[0]))
            elif isinstance(g, (Point, LineString)):
                self.assertEqual(1, g.num_geom)
                self.assertEqual(0, len(g))
            else:
                self.assertEqual(0, g.num_geom)
                self.assertEqual(0, len(g))

            # Testing __getitem__ (doesn't work on Point or Polygon)
            if isinstance(g, Point):
                self.assertRaises(GEOSIndexError, g.get_x)
            elif isinstance(g, Polygon):
                lr = g.shell
                self.assertEqual('LINEARRING EMPTY', lr.wkt)
                self.assertEqual(0, len(lr))
                self.assertEqual(True, lr.empty)
                self.assertRaises(GEOSIndexError, lr.__getitem__, 0)
            else:
                self.assertRaises(GEOSIndexError, g.__getitem__, 0)

    def test21_test_gdal(self):
        "Testing `ogr` and `srs` properties."
        if not HAS_GDAL: return
        g1 = fromstr('POINT(5 23)')
        self.assertEqual(True, isinstance(g1.ogr, OGRGeometry))
        self.assertEqual(g1.srs, None)
        
        g2 = fromstr('LINESTRING(0 0, 5 5, 23 23)', srid=4326)
        self.assertEqual(True, isinstance(g2.ogr, OGRGeometry))
        self.assertEqual(True, isinstance(g2.srs, SpatialReference))
        self.assertEqual(g2.hex, g2.ogr.hex)
        self.assertEqual('WGS 84', g2.srs.name)
        
def suite():
    s = unittest.TestSuite()
    s.addTest(unittest.makeSuite(GEOSTest))
    return s

def run(verbosity=2):
    unittest.TextTestRunner(verbosity=verbosity).run(suite())