Add jwt_token_creds test case to interop test for c++
diff --git a/tools/gce_setup/cloud_prod_runner.sh b/tools/gce_setup/cloud_prod_runner.sh
index 3a9ae51..e236c92 100755
--- a/tools/gce_setup/cloud_prod_runner.sh
+++ b/tools/gce_setup/cloud_prod_runner.sh
@@ -36,7 +36,7 @@
 main() {
   source grpc_docker.sh
   test_cases=(large_unary empty_unary ping_pong client_streaming server_streaming cancel_after_begin cancel_after_first_response)
-  auth_test_cases=(service_account_creds compute_engine_creds)
+  auth_test_cases=(service_account_creds compute_engine_creds jwt_token_creds)
   clients=(cxx java go ruby node csharp_mono)
   for test_case in "${test_cases[@]}"
   do
diff --git a/tools/gce_setup/grpc_docker.sh b/tools/gce_setup/grpc_docker.sh
index 3deef05..d6cbf0a 100755
--- a/tools/gce_setup/grpc_docker.sh
+++ b/tools/gce_setup/grpc_docker.sh
@@ -1192,6 +1192,20 @@
     echo $the_cmd
 }
 
+# constructs the full dockerized cpp jwt_token auth interop test cmd.
+#
+# call-seq:
+#   flags= .... # generic flags to include the command
+#   cmd=$($grpc_gen_test_cmd $flags)
+grpc_cloud_prod_auth_jwt_token_creds_gen_cxx_cmd() {
+    local cmd_prefix="sudo docker run grpc/cxx";
+    local test_script="/var/local/git/grpc/bins/opt/interop_client --enable_ssl --use_prod_roots";
+    local gfe_flags=$(_grpc_prod_gfe_flags)
+    local added_gfe_flags=$(_grpc_jwt_token_test_flags)
+    local the_cmd="$cmd_prefix $test_script $gfe_flags $added_gfe_flags $@";
+    echo $the_cmd
+}
+
 # constructs the full dockerized csharp-mono interop test cmd.
 #
 # call-seq:
@@ -1230,6 +1244,11 @@
   echo " --service_account_key_file=/service_account/stubbyCloudTestingTest-7dd63462c60c.json --oauth_scope=https://www.googleapis.com/auth/xapi.zoo"
 }
 
+# outputs the flags passed to the service account auth tests
+_grpc_jwt_token_test_flags() {
+  echo " --service_account_key_file=/service_account/stubbyCloudTestingTest-7dd63462c60c.json"
+}
+
 # default credentials test flag
 _grpc_default_creds_test_flags() {
   echo " --oauth_scope=https://www.googleapis.com/auth/xapi.zoo"