support no obstacle in RRT* (#375)

tests/test_rrt_star.py

@@ -20,7 +20,18 @@ class Test(TestCase):
         m.show_animation = False
         m.main()
 
+    def test_no_obstacle(self):
+        obstacle_list = []
+
+        # Set Initial parameters
+        rrt_star = m.RRTStar(start=[0, 0],
+                             goal=[6, 10],
+                             rand_area=[-2, 15],
+                             obstacle_list=obstacle_list)
+        path = rrt_star.planning(animation=False)
+        assert path is not None
 
 if __name__ == '__main__':  # pragma: no cover
     test = Test()
     test.test1()
+    test.test_no_obstacle()