--- a
+++ b/tests/test.simbody.py
@@ -0,0 +1,27 @@
+from osim.env import ProstheticsEnv
+import numpy as np
+import unittest
+
+class SimulationTest(unittest.TestCase):
+    def test1(self):
+        
+        env = ProstheticsEnv(visualize=True)
+        observation = env.reset()
+
+        simbody_state = env.osim_model.get_state()
+        print(simbody_state.getNumSubsystems())
+        print(simbody_state.getY())
+        oldy = simbody_state.updY()
+        for i in range(len(oldy)):
+            oldy[i] += 0.2
+        print(simbody_state.getY())
+        env.osim_model.set_state(simbody_state)
+
+        action = env.action_space.sample()
+
+        for i in range(50):
+            env.step(action)
+
+
+if __name__ == '__main__':
+    unittest.main()