diff --git a/test/test_node.rb b/test/test_node.rb
index 8f249e2..9d1acb0 100755
--- a/test/test_node.rb
+++ b/test/test_node.rb
@@ -135,6 +135,7 @@ def test_param_private
 
     node.set_param('~param2', 10)
     assert_equal(10, node.get_param('/hoge/param2'))
+    assert(node.delete_param('~param1'))
     assert(node.delete_param('~param2'))
     node.shutdown
   end
@@ -176,9 +177,7 @@ def test_sim_time
     param = ROS::ParameterManager.new(ENV['ROS_MASTER_URI'], '/use_sim_time', {})
     param.set_param('/use_sim_time', true)
 
-    while not param.get_param('/use_sim_time')
-      sleep 0.5
-    end
+    assert(param.get_param('/use_sim_time'))
 
     clock_node = ROS::Node.new('/clock')
     clock_pub = clock_node.advertise('/clock', Rosgraph_msgs::Clock)
@@ -196,6 +195,8 @@ def test_sim_time
     assert_equal(time_msg.clock, sim_current)
     param.delete_param('/use_sim_time')
 
+    assert(!param.get_param('/use_sim_time'))
+
     ROS::Time.initialize_with_sim_or_wall(node)
     node.shutdown
     clock_node.shutdown