diff --git a/tests/scripts/thread-cert/Cert_5_1_01_RouterAttach.py b/tests/scripts/thread-cert/Cert_5_1_01_RouterAttach.py
index e9acf810b..fd9ca3baf 100755
--- a/tests/scripts/thread-cert/Cert_5_1_01_RouterAttach.py
+++ b/tests/scripts/thread-cert/Cert_5_1_01_RouterAttach.py
@@ -62,8 +62,8 @@ class Cert_5_1_01_RouterAttach(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_02_ChildAddressTimeout.py b/tests/scripts/thread-cert/Cert_5_1_02_ChildAddressTimeout.py
index 0c7fba037..e130ae350 100755
--- a/tests/scripts/thread-cert/Cert_5_1_02_ChildAddressTimeout.py
+++ b/tests/scripts/thread-cert/Cert_5_1_02_ChildAddressTimeout.py
@@ -78,8 +78,8 @@ class Cert_5_1_02_ChildAddressTimeout(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_03_RouterAddressReallocation.py b/tests/scripts/thread-cert/Cert_5_1_03_RouterAddressReallocation.py
index fcf96520a..67045520c 100755
--- a/tests/scripts/thread-cert/Cert_5_1_03_RouterAddressReallocation.py
+++ b/tests/scripts/thread-cert/Cert_5_1_03_RouterAddressReallocation.py
@@ -72,8 +72,8 @@ class Cert_5_1_03_RouterAddressReallocation(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_04_RouterAddressReallocation.py b/tests/scripts/thread-cert/Cert_5_1_04_RouterAddressReallocation.py
index e1318d432..190e94125 100755
--- a/tests/scripts/thread-cert/Cert_5_1_04_RouterAddressReallocation.py
+++ b/tests/scripts/thread-cert/Cert_5_1_04_RouterAddressReallocation.py
@@ -72,8 +72,8 @@ class Cert_5_1_04_RouterAddressReallocation(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_05_RouterAddressTimeout.py b/tests/scripts/thread-cert/Cert_5_1_05_RouterAddressTimeout.py
index cce38a959..cacbf28d0 100755
--- a/tests/scripts/thread-cert/Cert_5_1_05_RouterAddressTimeout.py
+++ b/tests/scripts/thread-cert/Cert_5_1_05_RouterAddressTimeout.py
@@ -65,8 +65,8 @@ class Cert_5_1_05_RouterAddressTimeout(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_06_RemoveRouterId.py b/tests/scripts/thread-cert/Cert_5_1_06_RemoveRouterId.py
index 663d8b264..780e4f6e1 100755
--- a/tests/scripts/thread-cert/Cert_5_1_06_RemoveRouterId.py
+++ b/tests/scripts/thread-cert/Cert_5_1_06_RemoveRouterId.py
@@ -62,8 +62,8 @@ class Cert_5_1_06_RemoveRouterId(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_07_MaxChildCount.py b/tests/scripts/thread-cert/Cert_5_1_07_MaxChildCount.py
index 265672ca5..d6833e71a 100755
--- a/tests/scripts/thread-cert/Cert_5_1_07_MaxChildCount.py
+++ b/tests/scripts/thread-cert/Cert_5_1_07_MaxChildCount.py
@@ -71,8 +71,8 @@ class Cert_5_1_07_MaxChildCount(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_08_RouterAttachConnectivity.py b/tests/scripts/thread-cert/Cert_5_1_08_RouterAttachConnectivity.py
index 54c87f1da..e2fc82b1c 100755
--- a/tests/scripts/thread-cert/Cert_5_1_08_RouterAttachConnectivity.py
+++ b/tests/scripts/thread-cert/Cert_5_1_08_RouterAttachConnectivity.py
@@ -89,8 +89,8 @@ class Cert_5_1_08_RouterAttachConnectivity(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_09_REEDAttachConnectivity.py b/tests/scripts/thread-cert/Cert_5_1_09_REEDAttachConnectivity.py
index 7eef2474e..d75bff772 100755
--- a/tests/scripts/thread-cert/Cert_5_1_09_REEDAttachConnectivity.py
+++ b/tests/scripts/thread-cert/Cert_5_1_09_REEDAttachConnectivity.py
@@ -89,8 +89,8 @@ class Cert_5_1_09_REEDAttachConnectivity(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_10_RouterAttachLinkQuality.py b/tests/scripts/thread-cert/Cert_5_1_10_RouterAttachLinkQuality.py
index 0052e1e66..b26199a54 100755
--- a/tests/scripts/thread-cert/Cert_5_1_10_RouterAttachLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_5_1_10_RouterAttachLinkQuality.py
@@ -79,8 +79,8 @@ class Cert_5_1_10_RouterAttachLinkQuality(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_11_REEDAttachLinkQuality.py b/tests/scripts/thread-cert/Cert_5_1_11_REEDAttachLinkQuality.py
index f03be3302..d6417ecc6 100755
--- a/tests/scripts/thread-cert/Cert_5_1_11_REEDAttachLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_5_1_11_REEDAttachLinkQuality.py
@@ -79,8 +79,8 @@ class Cert_5_1_11_REEDAttachLinkQuality(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_1_12_NewRouterNeighborSync.py b/tests/scripts/thread-cert/Cert_5_1_12_NewRouterNeighborSync.py
index 3e2c80cf3..7344deea5 100755
--- a/tests/scripts/thread-cert/Cert_5_1_12_NewRouterNeighborSync.py
+++ b/tests/scripts/thread-cert/Cert_5_1_12_NewRouterNeighborSync.py
@@ -69,8 +69,8 @@ class Cert_5_1_12_NewRouterSync(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def verify_step_4(self, router1_messages, router2_messages, req_receiver, accept_receiver):
         if router2_messages.contains_mle_message(mle.CommandType.LINK_REQUEST) and \
diff --git a/tests/scripts/thread-cert/Cert_5_1_13_RouterReset.py b/tests/scripts/thread-cert/Cert_5_1_13_RouterReset.py
index 7383666f7..02b0fb4bc 100755
--- a/tests/scripts/thread-cert/Cert_5_1_13_RouterReset.py
+++ b/tests/scripts/thread-cert/Cert_5_1_13_RouterReset.py
@@ -64,8 +64,8 @@ class Cert_5_1_13_RouterReset(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_2_01_REEDAttach.py b/tests/scripts/thread-cert/Cert_5_2_01_REEDAttach.py
index 11c0344bd..acd1afc77 100755
--- a/tests/scripts/thread-cert/Cert_5_2_01_REEDAttach.py
+++ b/tests/scripts/thread-cert/Cert_5_2_01_REEDAttach.py
@@ -79,8 +79,8 @@ class Cert_5_2_01_REEDAttach(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_2_03_LeaderReject2Hops.py b/tests/scripts/thread-cert/Cert_5_2_03_LeaderReject2Hops.py
index 82bbfac18..82148c384 100755
--- a/tests/scripts/thread-cert/Cert_5_2_03_LeaderReject2Hops.py
+++ b/tests/scripts/thread-cert/Cert_5_2_03_LeaderReject2Hops.py
@@ -77,8 +77,8 @@ class Cert_5_2_3_LeaderReject2Hops(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1
diff --git a/tests/scripts/thread-cert/Cert_5_2_04_REEDUpgrade.py b/tests/scripts/thread-cert/Cert_5_2_04_REEDUpgrade.py
index a4667bec1..e9987d491 100755
--- a/tests/scripts/thread-cert/Cert_5_2_04_REEDUpgrade.py
+++ b/tests/scripts/thread-cert/Cert_5_2_04_REEDUpgrade.py
@@ -81,8 +81,8 @@ class Cert_5_2_4_REEDUpgrade(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1 Ensure topology is formed correctly without the DUT_REED.
diff --git a/tests/scripts/thread-cert/Cert_5_2_05_AddressQuery.py b/tests/scripts/thread-cert/Cert_5_2_05_AddressQuery.py
index ff9bc7b39..99bbb5f19 100755
--- a/tests/scripts/thread-cert/Cert_5_2_05_AddressQuery.py
+++ b/tests/scripts/thread-cert/Cert_5_2_05_AddressQuery.py
@@ -76,8 +76,8 @@ class Cert_5_2_5_AddressQuery(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1. LEADER: DHCPv6 Server for prefix 2001::/64.
diff --git a/tests/scripts/thread-cert/Cert_5_2_06_RouterDowngrade.py b/tests/scripts/thread-cert/Cert_5_2_06_RouterDowngrade.py
index 9c56c41c5..e016b543c 100755
--- a/tests/scripts/thread-cert/Cert_5_2_06_RouterDowngrade.py
+++ b/tests/scripts/thread-cert/Cert_5_2_06_RouterDowngrade.py
@@ -57,8 +57,8 @@ class Cert_5_2_06_RouterDowngrade(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1 Ensure topology is formed correctly without ROUTER24.
diff --git a/tests/scripts/thread-cert/Cert_5_2_07_REEDSynchronization.py b/tests/scripts/thread-cert/Cert_5_2_07_REEDSynchronization.py
index b2b54d622..1ad339893 100755
--- a/tests/scripts/thread-cert/Cert_5_2_07_REEDSynchronization.py
+++ b/tests/scripts/thread-cert/Cert_5_2_07_REEDSynchronization.py
@@ -54,8 +54,8 @@ class Cert_5_2_7_REEDSynchronization(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1. Ensure topology is formed correctly without DUT_ROUTER1.
diff --git a/tests/scripts/thread-cert/Cert_5_3_01_LinkLocal.py b/tests/scripts/thread-cert/Cert_5_3_01_LinkLocal.py
index 73c316184..95adcbcaf 100755
--- a/tests/scripts/thread-cert/Cert_5_3_01_LinkLocal.py
+++ b/tests/scripts/thread-cert/Cert_5_3_01_LinkLocal.py
@@ -55,8 +55,8 @@ class Cert_5_3_1_LinkLocal(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1
diff --git a/tests/scripts/thread-cert/Cert_5_3_02_RealmLocal.py b/tests/scripts/thread-cert/Cert_5_3_02_RealmLocal.py
index 477ff32d3..22221bfbc 100755
--- a/tests/scripts/thread-cert/Cert_5_3_02_RealmLocal.py
+++ b/tests/scripts/thread-cert/Cert_5_3_02_RealmLocal.py
@@ -75,8 +75,8 @@ class Cert_5_3_2_RealmLocal(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1
diff --git a/tests/scripts/thread-cert/Cert_5_3_03_AddressQuery.py b/tests/scripts/thread-cert/Cert_5_3_03_AddressQuery.py
index 7910a87d3..914baa7d0 100755
--- a/tests/scripts/thread-cert/Cert_5_3_03_AddressQuery.py
+++ b/tests/scripts/thread-cert/Cert_5_3_03_AddressQuery.py
@@ -86,8 +86,8 @@ class Cert_5_3_3_AddressQuery(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1
diff --git a/tests/scripts/thread-cert/Cert_5_3_04_AddressMapCache.py b/tests/scripts/thread-cert/Cert_5_3_04_AddressMapCache.py
index e5d888857..d454c566a 100755
--- a/tests/scripts/thread-cert/Cert_5_3_04_AddressMapCache.py
+++ b/tests/scripts/thread-cert/Cert_5_3_04_AddressMapCache.py
@@ -85,8 +85,8 @@ class Cert_5_3_4_AddressMapCache(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1
diff --git a/tests/scripts/thread-cert/Cert_5_3_05_RoutingLinkQuality.py b/tests/scripts/thread-cert/Cert_5_3_05_RoutingLinkQuality.py
index ee901451b..7938e4909 100755
--- a/tests/scripts/thread-cert/Cert_5_3_05_RoutingLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_5_3_05_RoutingLinkQuality.py
@@ -77,8 +77,8 @@ class Cert_5_3_5_RoutingLinkQuality(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1
diff --git a/tests/scripts/thread-cert/Cert_5_3_06_RouterIdMask.py b/tests/scripts/thread-cert/Cert_5_3_06_RouterIdMask.py
index 1d6c68ade..bfb27d294 100755
--- a/tests/scripts/thread-cert/Cert_5_3_06_RouterIdMask.py
+++ b/tests/scripts/thread-cert/Cert_5_3_06_RouterIdMask.py
@@ -71,8 +71,8 @@ class Cert_5_3_6_RouterIdMask(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1
diff --git a/tests/scripts/thread-cert/Cert_5_3_06b_RouterIdMask.py b/tests/scripts/thread-cert/Cert_5_3_06b_RouterIdMask.py
index b7f0aaa38..a4c05df28 100755
--- a/tests/scripts/thread-cert/Cert_5_3_06b_RouterIdMask.py
+++ b/tests/scripts/thread-cert/Cert_5_3_06b_RouterIdMask.py
@@ -66,8 +66,8 @@ class Cert_5_3_6_RouterIdMask(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_3_07_DuplicateAddress.py b/tests/scripts/thread-cert/Cert_5_3_07_DuplicateAddress.py
index 58fd9831a..af9c36974 100755
--- a/tests/scripts/thread-cert/Cert_5_3_07_DuplicateAddress.py
+++ b/tests/scripts/thread-cert/Cert_5_3_07_DuplicateAddress.py
@@ -91,8 +91,8 @@ class Cert_5_3_7_DuplicateAddress(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1
diff --git a/tests/scripts/thread-cert/Cert_5_3_08_ChildAddressSet.py b/tests/scripts/thread-cert/Cert_5_3_08_ChildAddressSet.py
index 041665359..6926ff086 100755
--- a/tests/scripts/thread-cert/Cert_5_3_08_ChildAddressSet.py
+++ b/tests/scripts/thread-cert/Cert_5_3_08_ChildAddressSet.py
@@ -73,8 +73,8 @@ class Cert_5_3_8_ChildAddressSet(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[DUT_LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_3_09_AddressQuery.py b/tests/scripts/thread-cert/Cert_5_3_09_AddressQuery.py
index 37c1a4268..9a913c911 100755
--- a/tests/scripts/thread-cert/Cert_5_3_09_AddressQuery.py
+++ b/tests/scripts/thread-cert/Cert_5_3_09_AddressQuery.py
@@ -86,8 +86,8 @@ class Cert_5_3_09_AddressQuery(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1 & 2 ALL: Build and verify the topology
diff --git a/tests/scripts/thread-cert/Cert_5_3_10_AddressQuery.py b/tests/scripts/thread-cert/Cert_5_3_10_AddressQuery.py
index c23c391a1..379206850 100755
--- a/tests/scripts/thread-cert/Cert_5_3_10_AddressQuery.py
+++ b/tests/scripts/thread-cert/Cert_5_3_10_AddressQuery.py
@@ -88,8 +88,8 @@ class Cert_5_3_10_AddressQuery(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1 & 2
diff --git a/tests/scripts/thread-cert/Cert_5_3_11_AddressQueryTimeoutIntervals.py b/tests/scripts/thread-cert/Cert_5_3_11_AddressQueryTimeoutIntervals.py
index 2697f1cef..4a9314ffd 100755
--- a/tests/scripts/thread-cert/Cert_5_3_11_AddressQueryTimeoutIntervals.py
+++ b/tests/scripts/thread-cert/Cert_5_3_11_AddressQueryTimeoutIntervals.py
@@ -66,8 +66,8 @@ class Cert_5_3_11_AddressQueryTimeoutIntervals(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1 ALL: Build and verify the topology
diff --git a/tests/scripts/thread-cert/Cert_5_5_01_LeaderReboot.py b/tests/scripts/thread-cert/Cert_5_5_01_LeaderReboot.py
index b4106fe04..5ed43257d 100755
--- a/tests/scripts/thread-cert/Cert_5_5_01_LeaderReboot.py
+++ b/tests/scripts/thread-cert/Cert_5_5_01_LeaderReboot.py
@@ -64,8 +64,8 @@ class Cert_5_5_1_LeaderReboot(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         # 1 ALL: Build and verify the topology
diff --git a/tests/scripts/thread-cert/Cert_5_5_02_LeaderReboot.py b/tests/scripts/thread-cert/Cert_5_5_02_LeaderReboot.py
index 403edc322..5e526992a 100755
--- a/tests/scripts/thread-cert/Cert_5_5_02_LeaderReboot.py
+++ b/tests/scripts/thread-cert/Cert_5_5_02_LeaderReboot.py
@@ -69,8 +69,8 @@ class Cert_5_5_2_LeaderReboot(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_5_03_SplitMergeChildren.py b/tests/scripts/thread-cert/Cert_5_5_03_SplitMergeChildren.py
index bad45596a..2e4ecd96f 100755
--- a/tests/scripts/thread-cert/Cert_5_5_03_SplitMergeChildren.py
+++ b/tests/scripts/thread-cert/Cert_5_5_03_SplitMergeChildren.py
@@ -93,8 +93,8 @@ class Cert_5_5_3_SplitMergeChildren(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_5_04_SplitMergeRouters.py b/tests/scripts/thread-cert/Cert_5_5_04_SplitMergeRouters.py
index 80d43d3f9..c31a0d36a 100755
--- a/tests/scripts/thread-cert/Cert_5_5_04_SplitMergeRouters.py
+++ b/tests/scripts/thread-cert/Cert_5_5_04_SplitMergeRouters.py
@@ -86,8 +86,8 @@ class Cert_5_5_4_SplitMergeRouters(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_5_05_SplitMergeREED.py b/tests/scripts/thread-cert/Cert_5_5_05_SplitMergeREED.py
index b8e5bcd8a..b8f1a17c4 100755
--- a/tests/scripts/thread-cert/Cert_5_5_05_SplitMergeREED.py
+++ b/tests/scripts/thread-cert/Cert_5_5_05_SplitMergeREED.py
@@ -78,8 +78,8 @@ class Cert_5_5_5_SplitMergeREED(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_5_07_SplitMergeThreeWay.py b/tests/scripts/thread-cert/Cert_5_5_07_SplitMergeThreeWay.py
index ec68df2ef..204de9063 100755
--- a/tests/scripts/thread-cert/Cert_5_5_07_SplitMergeThreeWay.py
+++ b/tests/scripts/thread-cert/Cert_5_5_07_SplitMergeThreeWay.py
@@ -78,8 +78,8 @@ class Cert_5_5_7_SplitMergeThreeWay(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER1].start()
diff --git a/tests/scripts/thread-cert/Cert_5_5_08_SplitRoutersLostLeader.py b/tests/scripts/thread-cert/Cert_5_5_08_SplitRoutersLostLeader.py
index c8dcee177..24c44fde6 100755
--- a/tests/scripts/thread-cert/Cert_5_5_08_SplitRoutersLostLeader.py
+++ b/tests/scripts/thread-cert/Cert_5_5_08_SplitRoutersLostLeader.py
@@ -87,7 +87,7 @@ class Cert_5_5_8_SplitRoutersLostLeader(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
+            node.destroy()
 
     def test(self):
         self.nodes[LEADER1].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_01_NetworkDataRegisterBeforeAttachLeader.py b/tests/scripts/thread-cert/Cert_5_6_01_NetworkDataRegisterBeforeAttachLeader.py
index 06bf9b534..9b52d7190 100755
--- a/tests/scripts/thread-cert/Cert_5_6_01_NetworkDataRegisterBeforeAttachLeader.py
+++ b/tests/scripts/thread-cert/Cert_5_6_01_NetworkDataRegisterBeforeAttachLeader.py
@@ -75,8 +75,8 @@ class Cert_5_6_1_NetworkDataLeaderAsBr(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_02_NetworkDataRegisterBeforeAttachRouter.py b/tests/scripts/thread-cert/Cert_5_6_02_NetworkDataRegisterBeforeAttachRouter.py
index 374f5664a..6f8a17c74 100755
--- a/tests/scripts/thread-cert/Cert_5_6_02_NetworkDataRegisterBeforeAttachRouter.py
+++ b/tests/scripts/thread-cert/Cert_5_6_02_NetworkDataRegisterBeforeAttachRouter.py
@@ -75,8 +75,8 @@ class Cert_5_6_2_NetworkDataRouterAsBr(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_03_NetworkDataRegisterAfterAttachLeader.py b/tests/scripts/thread-cert/Cert_5_6_03_NetworkDataRegisterAfterAttachLeader.py
index 9a4a0b61b..81d7d680c 100755
--- a/tests/scripts/thread-cert/Cert_5_6_03_NetworkDataRegisterAfterAttachLeader.py
+++ b/tests/scripts/thread-cert/Cert_5_6_03_NetworkDataRegisterAfterAttachLeader.py
@@ -75,8 +75,8 @@ class Cert_5_6_3_NetworkDataRegisterAfterAttachLeader(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_04_NetworkDataRegisterAfterAttachRouter.py b/tests/scripts/thread-cert/Cert_5_6_04_NetworkDataRegisterAfterAttachRouter.py
index ca7ec4ebd..900d27e5b 100755
--- a/tests/scripts/thread-cert/Cert_5_6_04_NetworkDataRegisterAfterAttachRouter.py
+++ b/tests/scripts/thread-cert/Cert_5_6_04_NetworkDataRegisterAfterAttachRouter.py
@@ -75,8 +75,8 @@ class Cert_5_6_4_NetworkDataRegisterAfterAttachRouter(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_05_NetworkDataRegisterAfterAttachRouter.py b/tests/scripts/thread-cert/Cert_5_6_05_NetworkDataRegisterAfterAttachRouter.py
index e40ed5681..00a673b8e 100755
--- a/tests/scripts/thread-cert/Cert_5_6_05_NetworkDataRegisterAfterAttachRouter.py
+++ b/tests/scripts/thread-cert/Cert_5_6_05_NetworkDataRegisterAfterAttachRouter.py
@@ -75,8 +75,8 @@ class Cert_5_6_5_NetworkDataRegisterAfterAttachRouter(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_06_NetworkDataExpiration.py b/tests/scripts/thread-cert/Cert_5_6_06_NetworkDataExpiration.py
index 2b17c0186..a67d093ba 100755
--- a/tests/scripts/thread-cert/Cert_5_6_06_NetworkDataExpiration.py
+++ b/tests/scripts/thread-cert/Cert_5_6_06_NetworkDataExpiration.py
@@ -75,8 +75,8 @@ class Cert_5_6_6_NetworkDataExpiration(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_07_NetworkDataRequestREED.py b/tests/scripts/thread-cert/Cert_5_6_07_NetworkDataRequestREED.py
index aa09d9774..636a4b1f2 100755
--- a/tests/scripts/thread-cert/Cert_5_6_07_NetworkDataRequestREED.py
+++ b/tests/scripts/thread-cert/Cert_5_6_07_NetworkDataRequestREED.py
@@ -66,8 +66,8 @@ class Cert_5_6_7_NetworkDataRequestREED(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_08_ContextManagement.py b/tests/scripts/thread-cert/Cert_5_6_08_ContextManagement.py
index e606f7b10..0527a0caa 100755
--- a/tests/scripts/thread-cert/Cert_5_6_08_ContextManagement.py
+++ b/tests/scripts/thread-cert/Cert_5_6_08_ContextManagement.py
@@ -66,8 +66,8 @@ class Cert_5_6_8_ContextManagement(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_6_09_NetworkDataForwarding.py b/tests/scripts/thread-cert/Cert_5_6_09_NetworkDataForwarding.py
index 9e23b7e69..381d2f94d 100755
--- a/tests/scripts/thread-cert/Cert_5_6_09_NetworkDataForwarding.py
+++ b/tests/scripts/thread-cert/Cert_5_6_09_NetworkDataForwarding.py
@@ -83,8 +83,8 @@ class Cert_5_6_9_NetworkDataForwarding(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_8_01_KeySynchronization.py b/tests/scripts/thread-cert/Cert_5_8_01_KeySynchronization.py
index 9d44d1c37..ffa5735e8 100755
--- a/tests/scripts/thread-cert/Cert_5_8_01_KeySynchronization.py
+++ b/tests/scripts/thread-cert/Cert_5_8_01_KeySynchronization.py
@@ -59,8 +59,8 @@ class Cert_5_8_1_KeySynchronization(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_8_02_KeyIncrement.py b/tests/scripts/thread-cert/Cert_5_8_02_KeyIncrement.py
index 53527a6ef..cb8f2c59b 100755
--- a/tests/scripts/thread-cert/Cert_5_8_02_KeyIncrement.py
+++ b/tests/scripts/thread-cert/Cert_5_8_02_KeyIncrement.py
@@ -60,8 +60,8 @@ class Cert_5_8_2_KeyIncrement(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_5_8_03_KeyIncrementRollOver.py b/tests/scripts/thread-cert/Cert_5_8_03_KeyIncrementRollOver.py
index 9a7e1dbdf..43b180908 100755
--- a/tests/scripts/thread-cert/Cert_5_8_03_KeyIncrementRollOver.py
+++ b/tests/scripts/thread-cert/Cert_5_8_03_KeyIncrementRollOver.py
@@ -61,8 +61,8 @@ class Cert_5_8_3_KeyIncrementRollOver(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_1_01_RouterAttach.py b/tests/scripts/thread-cert/Cert_6_1_01_RouterAttach.py
index 12f6d1e73..fc179ab97 100755
--- a/tests/scripts/thread-cert/Cert_6_1_01_RouterAttach.py
+++ b/tests/scripts/thread-cert/Cert_6_1_01_RouterAttach.py
@@ -58,8 +58,8 @@ class Cert_6_1_1_RouterAttach(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach.py b/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach.py
index d934b086b..89cdd5860 100755
--- a/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach.py
+++ b/tests/scripts/thread-cert/Cert_6_1_02_REEDAttach.py
@@ -65,8 +65,8 @@ class Cert_6_1_2_REEDAttach(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_1_03_RouterAttachConnectivity.py b/tests/scripts/thread-cert/Cert_6_1_03_RouterAttachConnectivity.py
index c830025d5..06566facc 100755
--- a/tests/scripts/thread-cert/Cert_6_1_03_RouterAttachConnectivity.py
+++ b/tests/scripts/thread-cert/Cert_6_1_03_RouterAttachConnectivity.py
@@ -85,8 +85,8 @@ class Cert_6_1_3_RouterAttachConnectivity(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_1_04_REEDAttachConnectivity.py b/tests/scripts/thread-cert/Cert_6_1_04_REEDAttachConnectivity.py
index 0a2c24d89..8fe8eee5a 100755
--- a/tests/scripts/thread-cert/Cert_6_1_04_REEDAttachConnectivity.py
+++ b/tests/scripts/thread-cert/Cert_6_1_04_REEDAttachConnectivity.py
@@ -85,8 +85,8 @@ class Cert_6_1_4_REEDAttachConnectivity(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_1_05_RouterAttachLinkQuality.py b/tests/scripts/thread-cert/Cert_6_1_05_RouterAttachLinkQuality.py
index 772e55b28..010e60fa9 100755
--- a/tests/scripts/thread-cert/Cert_6_1_05_RouterAttachLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_6_1_05_RouterAttachLinkQuality.py
@@ -75,8 +75,8 @@ class Cert_6_1_5_RouterAttachLinkQuality(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality.py b/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality.py
index 13488ea60..076bda2b1 100755
--- a/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality.py
+++ b/tests/scripts/thread-cert/Cert_6_1_06_REEDAttachLinkQuality.py
@@ -75,8 +75,8 @@ class Cert_6_1_6_REEDAttachLinkQuality(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_1_07_EDSynchronization.py b/tests/scripts/thread-cert/Cert_6_1_07_EDSynchronization.py
index c7f48b341..bcbbd14f5 100755
--- a/tests/scripts/thread-cert/Cert_6_1_07_EDSynchronization.py
+++ b/tests/scripts/thread-cert/Cert_6_1_07_EDSynchronization.py
@@ -89,8 +89,8 @@ class Cert_6_1_7_EDSynchronization(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_2_01_NewPartition.py b/tests/scripts/thread-cert/Cert_6_2_01_NewPartition.py
index 7c893568b..8899626f5 100755
--- a/tests/scripts/thread-cert/Cert_6_2_01_NewPartition.py
+++ b/tests/scripts/thread-cert/Cert_6_2_01_NewPartition.py
@@ -65,8 +65,8 @@ class Cert_6_2_1_NewPartition(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_2_02_NewPartition.py b/tests/scripts/thread-cert/Cert_6_2_02_NewPartition.py
index c95f52ca6..823cfb917 100755
--- a/tests/scripts/thread-cert/Cert_6_2_02_NewPartition.py
+++ b/tests/scripts/thread-cert/Cert_6_2_02_NewPartition.py
@@ -76,8 +76,8 @@ class Cert_6_2_2_NewPartition(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_3_01_OrphanReattach.py b/tests/scripts/thread-cert/Cert_6_3_01_OrphanReattach.py
index ff76e4d8c..7e4de0e5f 100755
--- a/tests/scripts/thread-cert/Cert_6_3_01_OrphanReattach.py
+++ b/tests/scripts/thread-cert/Cert_6_3_01_OrphanReattach.py
@@ -66,8 +66,8 @@ class Cert_6_3_1_OrphanReattach(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_3_02_NetworkDataUpdate.py b/tests/scripts/thread-cert/Cert_6_3_02_NetworkDataUpdate.py
index 8bfb35a96..d02519b88 100755
--- a/tests/scripts/thread-cert/Cert_6_3_02_NetworkDataUpdate.py
+++ b/tests/scripts/thread-cert/Cert_6_3_02_NetworkDataUpdate.py
@@ -58,8 +58,8 @@ class Cert_6_3_2_NetworkDataUpdate(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_4_01_LinkLocal.py b/tests/scripts/thread-cert/Cert_6_4_01_LinkLocal.py
index e4339c9e1..f0495820a 100755
--- a/tests/scripts/thread-cert/Cert_6_4_01_LinkLocal.py
+++ b/tests/scripts/thread-cert/Cert_6_4_01_LinkLocal.py
@@ -57,8 +57,8 @@ class Cert_6_4_1_LinkLocal(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_4_02_RealmLocal.py b/tests/scripts/thread-cert/Cert_6_4_02_RealmLocal.py
index 2a0bd969d..4e7edef7c 100755
--- a/tests/scripts/thread-cert/Cert_6_4_02_RealmLocal.py
+++ b/tests/scripts/thread-cert/Cert_6_4_02_RealmLocal.py
@@ -65,8 +65,8 @@ class Cert_5_3_2_RealmLocal(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_5_01_ChildResetSynchronize.py b/tests/scripts/thread-cert/Cert_6_5_01_ChildResetSynchronize.py
index 265fb9115..6631f63c4 100755
--- a/tests/scripts/thread-cert/Cert_6_5_01_ChildResetSynchronize.py
+++ b/tests/scripts/thread-cert/Cert_6_5_01_ChildResetSynchronize.py
@@ -61,8 +61,8 @@ class Cert_6_5_1_ChildResetSynchronize(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_5_02_ChildResetReattach.py b/tests/scripts/thread-cert/Cert_6_5_02_ChildResetReattach.py
index 549102ad5..e90077768 100755
--- a/tests/scripts/thread-cert/Cert_6_5_02_ChildResetReattach.py
+++ b/tests/scripts/thread-cert/Cert_6_5_02_ChildResetReattach.py
@@ -60,8 +60,8 @@ class Cert_6_5_2_ChildResetReattach(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_6_01_KeyIncrement.py b/tests/scripts/thread-cert/Cert_6_6_01_KeyIncrement.py
index cc327a055..0fa6ae1eb 100755
--- a/tests/scripts/thread-cert/Cert_6_6_01_KeyIncrement.py
+++ b/tests/scripts/thread-cert/Cert_6_6_01_KeyIncrement.py
@@ -59,8 +59,8 @@ class Cert_6_6_1_KeyIncrement(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_6_6_02_KeyIncrementRollOver.py b/tests/scripts/thread-cert/Cert_6_6_02_KeyIncrementRollOver.py
index d37b052db..3b17eb6e4 100755
--- a/tests/scripts/thread-cert/Cert_6_6_02_KeyIncrementRollOver.py
+++ b/tests/scripts/thread-cert/Cert_6_6_02_KeyIncrementRollOver.py
@@ -60,8 +60,8 @@ class Cert_6_6_2_KeyIncrement1(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_7_1_01_BorderRouterAsLeader.py b/tests/scripts/thread-cert/Cert_7_1_01_BorderRouterAsLeader.py
index 23eda976e..cdd2eeb07 100755
--- a/tests/scripts/thread-cert/Cert_7_1_01_BorderRouterAsLeader.py
+++ b/tests/scripts/thread-cert/Cert_7_1_01_BorderRouterAsLeader.py
@@ -75,8 +75,8 @@ class Cert_7_1_1_BorderRouterAsLeader(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_7_1_02_BorderRouterAsRouter.py b/tests/scripts/thread-cert/Cert_7_1_02_BorderRouterAsRouter.py
index 1f7ff178e..aef3a6ae2 100755
--- a/tests/scripts/thread-cert/Cert_7_1_02_BorderRouterAsRouter.py
+++ b/tests/scripts/thread-cert/Cert_7_1_02_BorderRouterAsRouter.py
@@ -75,8 +75,8 @@ class Cert_7_1_2_BorderRouterAsRouter(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_7_1_03_BorderRouterAsLeader.py b/tests/scripts/thread-cert/Cert_7_1_03_BorderRouterAsLeader.py
index deaddb6b2..5618bfca3 100755
--- a/tests/scripts/thread-cert/Cert_7_1_03_BorderRouterAsLeader.py
+++ b/tests/scripts/thread-cert/Cert_7_1_03_BorderRouterAsLeader.py
@@ -75,8 +75,8 @@ class Cert_7_1_3_BorderRouterAsLeader(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_7_1_04_BorderRouterAsRouter.py b/tests/scripts/thread-cert/Cert_7_1_04_BorderRouterAsRouter.py
index 64c9462b6..817295128 100755
--- a/tests/scripts/thread-cert/Cert_7_1_04_BorderRouterAsRouter.py
+++ b/tests/scripts/thread-cert/Cert_7_1_04_BorderRouterAsRouter.py
@@ -75,8 +75,8 @@ class Cert_7_1_4_BorderRouterAsRouter(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_7_1_05_BorderRouterAsRouter.py b/tests/scripts/thread-cert/Cert_7_1_05_BorderRouterAsRouter.py
index 89ed2901f..53f0d552b 100755
--- a/tests/scripts/thread-cert/Cert_7_1_05_BorderRouterAsRouter.py
+++ b/tests/scripts/thread-cert/Cert_7_1_05_BorderRouterAsRouter.py
@@ -75,8 +75,8 @@ class Cert_7_1_5_BorderRouterAsRouter(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_8_1_01_Commissioning.py b/tests/scripts/thread-cert/Cert_8_1_01_Commissioning.py
index 2608b758c..8a7fd8a6f 100755
--- a/tests/scripts/thread-cert/Cert_8_1_01_Commissioning.py
+++ b/tests/scripts/thread-cert/Cert_8_1_01_Commissioning.py
@@ -55,8 +55,8 @@ class Cert_8_1_01_Commissioning(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[COMMISSIONER].interface_up()
diff --git a/tests/scripts/thread-cert/Cert_8_1_02_Commissioning.py b/tests/scripts/thread-cert/Cert_8_1_02_Commissioning.py
index 62b5b75f6..e54cff75b 100755
--- a/tests/scripts/thread-cert/Cert_8_1_02_Commissioning.py
+++ b/tests/scripts/thread-cert/Cert_8_1_02_Commissioning.py
@@ -55,8 +55,8 @@ class Cert_8_1_02_Commissioning(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[COMMISSIONER].interface_up()
diff --git a/tests/scripts/thread-cert/Cert_8_2_01_JoinerRouter.py b/tests/scripts/thread-cert/Cert_8_2_01_JoinerRouter.py
index 4d5f885dc..08b77d8a0 100755
--- a/tests/scripts/thread-cert/Cert_8_2_01_JoinerRouter.py
+++ b/tests/scripts/thread-cert/Cert_8_2_01_JoinerRouter.py
@@ -64,8 +64,8 @@ class Cert_8_2_01_JoinerRouter(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[COMMISSIONER].interface_up()
diff --git a/tests/scripts/thread-cert/Cert_8_2_02_JoinerRouter.py b/tests/scripts/thread-cert/Cert_8_2_02_JoinerRouter.py
index ea25b64b7..4be8d8e1b 100755
--- a/tests/scripts/thread-cert/Cert_8_2_02_JoinerRouter.py
+++ b/tests/scripts/thread-cert/Cert_8_2_02_JoinerRouter.py
@@ -64,8 +64,8 @@ class Cert_8_2_02_JoinerRouter(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[COMMISSIONER].interface_up()
diff --git a/tests/scripts/thread-cert/Cert_9_2_04_ActiveDataset.py b/tests/scripts/thread-cert/Cert_9_2_04_ActiveDataset.py
index ad69a6990..61b143bcf 100755
--- a/tests/scripts/thread-cert/Cert_9_2_04_ActiveDataset.py
+++ b/tests/scripts/thread-cert/Cert_9_2_04_ActiveDataset.py
@@ -55,8 +55,8 @@ class Cert_9_2_15_PendingPartition(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_07_DelayTimer.py b/tests/scripts/thread-cert/Cert_9_2_07_DelayTimer.py
index b15c63c35..bfc9fb000 100755
--- a/tests/scripts/thread-cert/Cert_9_2_07_DelayTimer.py
+++ b/tests/scripts/thread-cert/Cert_9_2_07_DelayTimer.py
@@ -80,8 +80,8 @@ class Cert_9_2_7_DelayTimer(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_08_PersistentDatasets.py b/tests/scripts/thread-cert/Cert_9_2_08_PersistentDatasets.py
index 35e582295..4bb5fff0a 100755
--- a/tests/scripts/thread-cert/Cert_9_2_08_PersistentDatasets.py
+++ b/tests/scripts/thread-cert/Cert_9_2_08_PersistentDatasets.py
@@ -102,7 +102,7 @@ class Cert_9_2_8_PersistentDatasets(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
+            node.destroy()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_09_PendingPartition.py b/tests/scripts/thread-cert/Cert_9_2_09_PendingPartition.py
index 7b0f51c21..a5736635e 100755
--- a/tests/scripts/thread-cert/Cert_9_2_09_PendingPartition.py
+++ b/tests/scripts/thread-cert/Cert_9_2_09_PendingPartition.py
@@ -83,8 +83,8 @@ class Cert_9_2_09_PendingPartition(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_10_PendingPartition.py b/tests/scripts/thread-cert/Cert_9_2_10_PendingPartition.py
index 63e3e7101..ee0107973 100755
--- a/tests/scripts/thread-cert/Cert_9_2_10_PendingPartition.py
+++ b/tests/scripts/thread-cert/Cert_9_2_10_PendingPartition.py
@@ -93,8 +93,8 @@ class Cert_9_2_10_PendingPartition(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_11_MasterKey.py b/tests/scripts/thread-cert/Cert_9_2_11_MasterKey.py
index ecf3b8b01..8d863bb54 100755
--- a/tests/scripts/thread-cert/Cert_9_2_11_MasterKey.py
+++ b/tests/scripts/thread-cert/Cert_9_2_11_MasterKey.py
@@ -94,8 +94,8 @@ class Cert_9_2_11_MasterKey(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_12_Announce.py b/tests/scripts/thread-cert/Cert_9_2_12_Announce.py
index fc313d829..bd29c483a 100755
--- a/tests/scripts/thread-cert/Cert_9_2_12_Announce.py
+++ b/tests/scripts/thread-cert/Cert_9_2_12_Announce.py
@@ -90,8 +90,8 @@ class Cert_9_2_12_Announce(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER1].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_13_EnergyScan.py b/tests/scripts/thread-cert/Cert_9_2_13_EnergyScan.py
index 3c070a8f7..31ee6fd99 100755
--- a/tests/scripts/thread-cert/Cert_9_2_13_EnergyScan.py
+++ b/tests/scripts/thread-cert/Cert_9_2_13_EnergyScan.py
@@ -73,8 +73,8 @@ class Cert_9_2_13_EnergyScan(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_14_PanIdQuery.py b/tests/scripts/thread-cert/Cert_9_2_14_PanIdQuery.py
index 1c4025180..da9fe9291 100755
--- a/tests/scripts/thread-cert/Cert_9_2_14_PanIdQuery.py
+++ b/tests/scripts/thread-cert/Cert_9_2_14_PanIdQuery.py
@@ -73,8 +73,8 @@ class Cert_9_2_14_PanIdQuery(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER1].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_15_PendingPartition.py b/tests/scripts/thread-cert/Cert_9_2_15_PendingPartition.py
index acd7f469f..87a38070e 100755
--- a/tests/scripts/thread-cert/Cert_9_2_15_PendingPartition.py
+++ b/tests/scripts/thread-cert/Cert_9_2_15_PendingPartition.py
@@ -84,8 +84,8 @@ class Cert_9_2_15_PendingPartition(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_16_ActivePendingPartition.py b/tests/scripts/thread-cert/Cert_9_2_16_ActivePendingPartition.py
index e5219d12f..0bf1c6fa6 100755
--- a/tests/scripts/thread-cert/Cert_9_2_16_ActivePendingPartition.py
+++ b/tests/scripts/thread-cert/Cert_9_2_16_ActivePendingPartition.py
@@ -85,8 +85,8 @@ class Cert_9_2_16_ActivePendingPartition(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_17_Orphan.py b/tests/scripts/thread-cert/Cert_9_2_17_Orphan.py
index 485c6d3f9..201b75918 100755
--- a/tests/scripts/thread-cert/Cert_9_2_17_Orphan.py
+++ b/tests/scripts/thread-cert/Cert_9_2_17_Orphan.py
@@ -71,8 +71,8 @@ class Cert_9_2_17_Orphan(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def test(self):
         self.nodes[LEADER1].start()
diff --git a/tests/scripts/thread-cert/Cert_9_2_18_RollBackActiveTimestamp.py b/tests/scripts/thread-cert/Cert_9_2_18_RollBackActiveTimestamp.py
index 43a81758e..f9cf62a8e 100755
--- a/tests/scripts/thread-cert/Cert_9_2_18_RollBackActiveTimestamp.py
+++ b/tests/scripts/thread-cert/Cert_9_2_18_RollBackActiveTimestamp.py
@@ -103,7 +103,7 @@ class Cert_9_2_18_RollBackActiveTimestamp(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
+            node.destroy()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/Makefile.am b/tests/scripts/thread-cert/Makefile.am
index 39c69d262..9adffddc3 100644
--- a/tests/scripts/thread-cert/Makefile.am
+++ b/tests/scripts/thread-cert/Makefile.am
@@ -134,6 +134,7 @@ EXTRA_DIST                                                         = \
     network_layer.py                                                 \
     node.py                                                          \
     node_cli.py                                                      \
+    pcap.py                                                          \
     simulator.py                                                     \
     sniffer.py                                                       \
     sniffer_transport.py                                             \
diff --git a/tests/scripts/thread-cert/Test_Cli.py b/tests/scripts/thread-cert/Test_Cli.py
index 49762d05e..368754827 100755
--- a/tests/scripts/thread-cert/Test_Cli.py
+++ b/tests/scripts/thread-cert/Test_Cli.py
@@ -42,7 +42,7 @@ class Cert_Cli(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
+            node.destroy()
 
     def test(self):
         commands = self.nodes[LEADER].get_commands()
diff --git a/tests/scripts/thread-cert/Test_MacScan.py b/tests/scripts/thread-cert/Test_MacScan.py
index 731420138..2adfc207a 100755
--- a/tests/scripts/thread-cert/Test_MacScan.py
+++ b/tests/scripts/thread-cert/Test_MacScan.py
@@ -58,7 +58,7 @@ class Test_MacScan(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
+            node.destroy()
 
     def test(self):
         self.nodes[LEADER].start()
diff --git a/tests/scripts/thread-cert/node.py b/tests/scripts/thread-cert/node.py
index 8f37cdf86..15265d8f1 100755
--- a/tests/scripts/thread-cert/node.py
+++ b/tests/scripts/thread-cert/node.py
@@ -51,7 +51,12 @@ class Node:
         self.interface.set_timeout(100)
 
     def __del__(self):
-        del self.interface
+        self.destroy()
+
+    def destroy(self):
+        if self.interface:
+            self.interface.destroy()
+            self.interface = None
 
     def set_mode(self, mode):
         self.interface.set_mode(mode)
diff --git a/tests/scripts/thread-cert/node_cli.py b/tests/scripts/thread-cert/node_cli.py
index 94538f3a5..2c5592a11 100644
--- a/tests/scripts/thread-cert/node_cli.py
+++ b/tests/scripts/thread-cert/node_cli.py
@@ -108,11 +108,15 @@ class otCli:
         self.pexpect = fdpexpect.fdspawn(os.open(serialPort, os.O_RDWR|os.O_NONBLOCK|os.O_NOCTTY))
 
     def __del__(self):
-        if self.pexpect.isalive():
+        self.destroy()
+
+    def destroy(self):
+        if self.pexpect and self.pexpect.isalive():
             self.send_command('exit')
             self.pexpect.expect(pexpect.EOF)
             self.pexpect.terminate()
             self.pexpect.close(force=True)
+            self.pexpect = None
 
     def send_command(self, cmd):
         print("%d: %s" % (self.nodeid, cmd))
diff --git a/tests/scripts/thread-cert/pcap.py b/tests/scripts/thread-cert/pcap.py
new file mode 100644
index 000000000..d90225abc
--- /dev/null
+++ b/tests/scripts/thread-cert/pcap.py
@@ -0,0 +1,69 @@
+#
+#  Copyright (c) 2018, The OpenThread Authors.
+#  All rights reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+""" Module to provide codec utilities for .pcap formatters. """
+
+import struct
+import time
+
+DLT_IEEE802_15_4 = 195
+PCAP_MAGIC_NUMBER = 0xa1b2c3d4
+PCAP_VERSION_MAJOR = 2
+PCAP_VERSION_MINOR = 4
+
+
+class PcapCodec(object):
+    """ Utility class for .pcap formatters. """
+
+    def __init__(self, filename):
+        self._pcap_file = open('%s.pcap' % filename, 'wb')
+        self._pcap_file.write(self.encode_header())
+        self._epoch = time.time()
+
+    def encode_header(self):
+        """ Returns a pcap file header. """
+        return struct.pack("<LHHLLLL",
+                           PCAP_MAGIC_NUMBER,
+                           PCAP_VERSION_MAJOR,
+                           PCAP_VERSION_MINOR,
+                           0, 0, 256,
+                           DLT_IEEE802_15_4)
+
+    def encode_frame(self, frame, sec, usec):
+        """ Returns a pcap encapsulation of the given frame. """
+        frame = frame[1:]
+        length = len(frame)
+        pcap_frame = struct.pack("<LLLL", sec, usec, length, length)
+        pcap_frame += frame
+        return pcap_frame
+
+    def _get_timestamp(self):
+        """ Returns the internal timestamp. """
+        timestamp = time.time() - self._epoch
+        timestamp_sec = int(timestamp)
+        timestamp_usec = int((timestamp - timestamp_sec) * 1000000)
+        return timestamp_sec, timestamp_usec
+
+    def append(self, frame, timestamp=None):
+        """ Appends a frame. """
+        if timestamp is None:
+            timestamp = self._get_timestamp()
+        pkt = self.encode_frame(frame, *timestamp)
+        self._pcap_file.write(pkt)
+
+    def __del__(self):
+        self._pcap_file.close()
diff --git a/tests/scripts/thread-cert/simulator.py b/tests/scripts/thread-cert/simulator.py
index 63e9ef65b..b84cd8f79 100644
--- a/tests/scripts/thread-cert/simulator.py
+++ b/tests/scripts/thread-cert/simulator.py
@@ -38,6 +38,7 @@ import sys
 import io
 import config
 import message
+import pcap
 
 class RealTime:
 
@@ -54,6 +55,9 @@ class RealTime:
     def go(self, duration):
         time.sleep(duration)
 
+    def stop(self):
+        pass
+
 class VirtualTime:
 
     BASE_PORT = 9000
@@ -73,10 +77,17 @@ class VirtualTime:
         self.current_time = 0
         self.current_event = None;
 
+        self._pcap = pcap.PcapCodec(os.getenv('TEST_NAME', 'current'))
+
         self._message_factory = config.create_default_thread_message_factory()
 
     def __del__(self):
+        if self.sock:
+            self.stop()
+
+    def stop(self):
         self.sock.close()
+        self.sock = None
 
     def _add_message(self, nodeid, message):
         addr = ('127.0.0.1', self.port + nodeid)
@@ -167,6 +178,7 @@ class VirtualTime:
                         #print "-- Enqueue\t", event
                         bisect.insort(self.event_queue, event)
 
+                self._pcap.append(data, (event_time // 1000000, event_time % 1000000))
                 self._add_message(addr[1] - self.port, data)
 
                 # add radio transmit done events to event queue
diff --git a/tests/scripts/thread-cert/sniffer.py b/tests/scripts/thread-cert/sniffer.py
index 6249166b2..c90d9bbea 100644
--- a/tests/scripts/thread-cert/sniffer.py
+++ b/tests/scripts/thread-cert/sniffer.py
@@ -30,6 +30,8 @@
 import collections
 import io
 import logging
+import os
+import pcap
 import threading
 
 try:
@@ -59,6 +61,8 @@ class Sniffer:
         self.nodeid = nodeid
         self._message_factory = message_factory
 
+        self._pcap = pcap.PcapCodec(os.getenv('TEST_NAME', 'current'))
+
         # Create transport
         transport_factory = sniffer_transport.SnifferTransportFactory()
         self._transport = transport_factory.create_transport(nodeid)
@@ -69,9 +73,6 @@ class Sniffer:
 
         self._buckets = collections.defaultdict(Queue.Queue)
 
-    def __del__(self):
-        del self._transport
-
     def _sniffer_main_loop(self):
         """ Sniffer main loop. """
 
@@ -80,6 +81,8 @@ class Sniffer:
         while self._thread_alive.is_set():
             data, nodeid = self._transport.recv(self.RECV_BUFFER_SIZE)
 
+            self._pcap.append(data)
+
             # Ignore any exceptions
             try:
                 msg = self._message_factory.create(io.BytesIO(data))
@@ -112,7 +115,7 @@ class Sniffer:
         self._thread_alive.clear()
 
         self._transport.close()
-        
+
         self._thread.join()
         self._thread = None
 
diff --git a/tests/scripts/thread-cert/test_service.py b/tests/scripts/thread-cert/test_service.py
index 6312f105e..e35a387fe 100755
--- a/tests/scripts/thread-cert/test_service.py
+++ b/tests/scripts/thread-cert/test_service.py
@@ -85,8 +85,8 @@ class Test_Service(unittest.TestCase):
     def tearDown(self):
         for node in list(self.nodes.values()):
             node.stop()
-        del self.nodes
-        del self.simulator
+            node.destroy()
+        self.simulator.stop()
 
     def hasAloc(self, node_id, service_id):
         for addr in self.nodes[node_id].get_ip6_address(config.ADDRESS_TYPE.ALOC):
diff --git a/third_party/openthread-test-driver/test-driver b/third_party/openthread-test-driver/test-driver
index 09eb6869f..29a68ecf0 100755
--- a/third_party/openthread-test-driver/test-driver
+++ b/third_party/openthread-test-driver/test-driver
@@ -116,7 +116,7 @@ while true; do
 done
 
 # Run a test
-PORT_OFFSET=$OFFSET "$@" >$log_file 2>&1
+TEST_NAME="${test_name}" PORT_OFFSET=$OFFSET "$@" >$log_file 2>&1
 estatus=$?
 
 # Return the offset