diff --git a/src/rest/resource.cpp b/src/rest/resource.cpp
index 865e1e6728b..def6a00ab23 100644
--- a/src/rest/resource.cpp
+++ b/src/rest/resource.cpp
@@ -123,11 +123,6 @@ Resource::Resource(ControllerOpenThread *aNcp)
     mResourceCallbackMap.emplace(OT_REST_RESOURCE_PATH_DIAGNOETIC, &Resource::HandleDiagnosticCallback);
 }
 
-void Resource::Init(void)
-{
-    otThreadSetReceiveDiagnosticGetCallback(mInstance, &Resource::DiagnosticResponseHandler, this);
-}
-
 void Resource::Handle(Request &aRequest, Response &aResponse) const
 {
     std::string url = aRequest.GetUrl();
@@ -518,31 +513,22 @@ void Resource::UpdateDiag(std::string aKey, std::vector<otNetworkDiagTlv> &aDiag
 
 void Resource::Diagnostic(const Request &aRequest, Response &aResponse) const
 {
-    otbrError error = OTBR_ERROR_NONE;
+    otThreadSetReceiveDiagnosticGetCallback(mInstance, &Resource::DiagnosticResponseHandler,
+                                            const_cast<Resource *>(this));
     OT_UNUSED_VARIABLE(aRequest);
     struct otIp6Address rloc16address = *otThreadGetRloc(mInstance);
     struct otIp6Address multicastAddress;
 
     VerifyOrExit(otThreadSendDiagnosticGet(mInstance, &rloc16address, kAllTlvTypes, sizeof(kAllTlvTypes)) ==
-                     OT_ERROR_NONE,
-                 error = OTBR_ERROR_REST);
-    VerifyOrExit(otIp6AddressFromString(kMulticastAddrAllRouters, &multicastAddress) == OT_ERROR_NONE,
-                 error = OTBR_ERROR_REST);
+                 OT_ERROR_NONE);
+    VerifyOrExit(otIp6AddressFromString(kMulticastAddrAllRouters, &multicastAddress) == OT_ERROR_NONE);
     VerifyOrExit(otThreadSendDiagnosticGet(mInstance, &multicastAddress, kAllTlvTypes, sizeof(kAllTlvTypes)) ==
-                     OT_ERROR_NONE,
-                 error = OTBR_ERROR_REST);
+                 OT_ERROR_NONE);
 
 exit:
 
-    if (error == OTBR_ERROR_NONE)
-    {
-        aResponse.SetStartTime(steady_clock::now());
-        aResponse.SetCallback();
-    }
-    else
-    {
-        ErrorHandler(aResponse, HttpStatusCode::kStatusInternalServerError);
-    }
+    aResponse.SetStartTime(steady_clock::now());
+    aResponse.SetCallback();
 }
 
 void Resource::DiagnosticResponseHandler(otMessage *aMessage, const otMessageInfo *aMessageInfo, void *aContext)
diff --git a/src/rest/resource.hpp b/src/rest/resource.hpp
index 80c9aca79b5..b818d7c913f 100644
--- a/src/rest/resource.hpp
+++ b/src/rest/resource.hpp
@@ -65,13 +65,6 @@ class Resource
      */
     Resource(ControllerOpenThread *aNcp);
 
-    /**
-     * This method initialize the Resource handler.
-     *
-     *
-     */
-    void Init(void);
-
     /**
      * This method is the main entry of resource handler, which find corresponding handler according to request url
      * find the resource and set the content of response.
diff --git a/src/rest/rest_web_server.cpp b/src/rest/rest_web_server.cpp
index a9c7964b481..120519016e2 100644
--- a/src/rest/rest_web_server.cpp
+++ b/src/rest/rest_web_server.cpp
@@ -61,8 +61,6 @@ otbrError RestWebServer::Init(void)
 {
     otbrError error = OTBR_ERROR_NONE;
 
-    mResource.Init();
-
     error = InitializeListenFd();
 
     return error;
diff --git a/tests/rest/CMakeLists.txt b/tests/rest/CMakeLists.txt
index e0899440b9d..f6ba89dc634 100644
--- a/tests/rest/CMakeLists.txt
+++ b/tests/rest/CMakeLists.txt
@@ -39,3 +39,7 @@ set_tests_properties(rest-server PROPERTIES
 set_tests_properties(rest-server PROPERTIES
                     LABELS "TESTREST" 
 )
+
+set_tests_properties(rest-server PROPERTIES
+                    TIMEOUT 60 
+)
diff --git a/tests/rest/test-rest-server b/tests/rest/test-rest-server
index 159c2348d50..1c30ca62013 100755
--- a/tests/rest/test-rest-server
+++ b/tests/rest/test-rest-server
@@ -48,6 +48,12 @@ main()
     sudo "${CMAKE_BINARY_DIR}"/src/agent/otbr-agent -d 7 -v -I wpan0 "spinel+hdlc+forkpty://$(command -v ot-rcp)?forkpty-arg=1" &
     trap on_exit EXIT
     sleep 5
+    sudo "${CMAKE_BINARY_DIR}"/third_party/openthread/repo/src/posix/ot-ctl factoryreset
+    sleep 1
+    sudo "${CMAKE_BINARY_DIR}"/third_party/openthread/repo/src/posix/ot-ctl ifconfig up
+    sleep 1
+    sudo "${CMAKE_BINARY_DIR}"/third_party/openthread/repo/src/posix/ot-ctl thread start
+    sleep 3
     sudo python3 "${CMAKE_CURRENT_SOURCE_DIR}"/test_rest.py
 }
 
diff --git a/tests/rest/test_rest.py b/tests/rest/test_rest.py
index dde32dd9752..3e6caa788bb 100644
--- a/tests/rest/test_rest.py
+++ b/tests/rest/test_rest.py
@@ -37,11 +37,17 @@
 
 
 def get_data_from_url(url, result, index):
-    response = urllib.request.urlopen(urllib.request.Request(url))
-    body = response.read()
-    data = json.loads(body)
-    result[index] = data
 
+    try:    
+        response = urllib.request.urlopen(urllib.request.Request(url))
+        body = response.read()
+        data = json.loads(body)
+        result[index] = data
+
+    
+    except urllib.error.HTTPError as e:
+        # Todo : print detail debug message from response
+        print(e.code)   
 
 def get_error_from_url(url, result, index):
     try: