Extend test.

tests/test.py

 """
   OPC-UA test agent used for testing of PLC program here: https://lab.nexedi.com/nexedi/osie/tree/master/Beremiz/beremiz_test_opc_ua
-  XXX:
-  - add asserts
+
 """
 from opcua import Client
 import time
 
-client = Client("opc.tcp://k2-osie:4840/")
+TIMEOUT = 5 # seconds to wait between checks
+NUMBER_OF_CHECKS = 10 # number of times we check the server
+OPC_UA_ADDRESS = "opc.tcp://k2-osie:4840/"
+OPC_UA_IDENTIFIER = "ns=1;s=i2c0.relay0"
+
+# connect to a session at OPC-UA server
+client = Client(OPC_UA_ADDRESS)
 
 try:
   client.connect()
@@ -14,13 +19,17 @@ try:
   # Client has a few methods to get proxy to UA nodes that should always be in address space such as Root or Objects
   root = client.get_root_node()
   children_list = root.get_children()
-  for i in range (0,10):
-    var = client.get_node("ns=1;s=i2c0.relay0")
-    i2c0_relay0 = var.get_value()
-    # XXX: do asserts here
-    print  i2c0_relay0
-    print "sleep"
-    time.sleep(5)
+  var = client.get_node(OPC_UA_IDENTIFIER)
+
+  for i in range (0, NUMBER_OF_CHECKS):
+    i2c0_relay0_before = var.get_value()
+    print "\ni2c0_relay0 (before) = ", i2c0_relay0_before
+    print "sleep ..."
+    time.sleep(TIMEOUT)
+    i2c0_relay0_after = var.get_value()
+    print "i2c0_relay0 (after) = ", i2c0_relay0_after
+    # for the wait timeout runtime should have increased the value
+    assert i2c0_relay0_after > i2c0_relay0_before
 
 finally:
   client.disconnect()