Added test for GEOSCoordSeq.__getitem__().

tests/gis_tests/geos_tests/test_coordseq.py

+from django.contrib.gis.geos import LineString
+from django.test import SimpleTestCase
+
+
+class GEOSCoordSeqTest(SimpleTestCase):
+
+    def test_getitem(self):
+        coord_seq = LineString([(x, x) for x in range(2)]).coord_seq
+        for i in (0, 1):
+            with self.subTest(i):
+                self.assertEqual(coord_seq[i], (i, i))
+        for i in (-3, 10):
+            msg = 'invalid GEOS Geometry index: %s' % i
+            with self.subTest(i):
+                with self.assertRaisesMessage(IndexError, msg):
+                    coord_seq[i]