check that rewards work (kind of)

tests/api_test.py

@@ -80,10 +80,15 @@ def test_step():
     done = False
     obs, info = env.reset()
     step = 0
+    _return = 0.0
     while not done:
-        obs, reward, term, trunc, info = env.step((0,0))
+        obs, reward, term, trunc, info = env.step((0, None))
         done = term or trunc
         print(obs, reward, done, info)
         step += 1
+        _return += reward
+
+    assert done
+    assert _return < 0.0 
+
 
-    assert done