diff --git a/dse/network/examples/stub/simulation.yaml b/dse/network/examples/stub/simulation.yaml
index 6b5f2a5..f1f21e9 100644
--- a/dse/network/examples/stub/simulation.yaml
+++ b/dse/network/examples/stub/simulation.yaml
@@ -49,6 +49,8 @@ spec:
     - signal: temperature
     - signal: schedule_signal
     - signal: foo_double
+    - signal: foo
+    - signal: alive
 ---
 kind: SignalGroup
 metadata:
diff --git a/dse/network/function.c b/dse/network/function.c
index 743c7b1..9e2debf 100644
--- a/dse/network/function.c
+++ b/dse/network/function.c
@@ -41,6 +41,8 @@ int network_function_apply_encode(Network* network)
             /* Trigger update of signals based on changed payload. */
             nm_p->update_signals = true;
 			nm_p->unpack_func(nm_p->buffer, nm_p->payload, nm_p->payload_len);
+            /* Set the buffer checksum to prevent subsequent Tx. */
+            nm_p->buffer_checksum = simbus_generate_uid_hash(nm_p->buffer, nm_p->buffer_len);
         }
     }
 
diff --git a/tests/cmocka/mstep/test_mstep.c b/tests/cmocka/mstep/test_mstep.c
index aaaebe8..e884080 100644
--- a/tests/cmocka/mstep/test_mstep.c
+++ b/tests/cmocka/mstep/test_mstep.c
@@ -63,7 +63,7 @@ void test_mstep(void** state)
 
     assert_non_null(model->sv_signal);
     assert_string_equal(model->sv_signal->name, "signal");
-    assert_int_equal(model->sv_signal->count, 5);
+    assert_int_equal(model->sv_signal->count, 7);
     assert_non_null(model->sv_signal->scalar);
     assert_non_null(model->sv_network);
     assert_string_equal(model->sv_network->name, "network");
@@ -111,7 +111,7 @@ void test_mstep(void** state)
     %02x %02x %02x\n", buffer[i+0], buffer[i+1], buffer[i+2], buffer[i+3],
             buffer[i+4], buffer[i+5], buffer[i+6], buffer[i+7]);
     }*/
-    size_t   C_len = 0x62;
+    size_t  C_len = 0x62;
     uint8_t C_buf[0x62];
     memcpy(C_buf, model->sv_network->binary[0], C_len);
     C_buf[53] = 0x42;
@@ -144,8 +144,88 @@ void test_mstep(void** state)
 
 void test_mstep_message_function(void** state)
 {
-    UNUSED(state);
-    skip();
+#define MSG_NF_NAME             "function_example"
+#define MSG_NF_FRAME_ID         0x1f2
+#define MSG_NF_FRAME_SIG_OFFSET 2
+#define MSG_NF_SIG_NAME         "foo"  // uint8_t
+#define MSG_NF_SIG_IDX          5
+#define MSG_NF_ALIVE_NAME       "alive"  // uint8_t
+#define MSG_NF_ALIVE_IDX        6
+#define NETWORK_NAME            "stub_inst"
+#define NETWORK_SIG             "can"
+
+    SimMock*   mock = *state;
+    ModelMock* network_model = &mock->model[0];
+    assert_non_null(network_model);
+    assert_true(MSG_NF_SIG_IDX < mock->sv_signal->count);
+    assert_true(MSG_NF_ALIVE_IDX < mock->sv_signal->count);
+
+    /* 0-5ms */
+    {
+        for (uint32_t i = 0; i < 10; i++) {
+            assert_int_equal(simmock_step(mock, true), 0);
+            assert_int_equal(network_model->sv_network->length[0] > 0,
+                false);  // can_bus has no data.
+        }
+    }
+    /* 5.5ms - Set a signal value. */
+    {
+        mock->sv_signal->scalar[MSG_NF_SIG_IDX] = 4;
+        assert_int_equal(simmock_step(mock, true), 0);
+        assert_int_equal(network_model->sv_network->length[0] > 0,
+            true);  // can_bus has data.
+        SignalCheck s_checks[] = {
+            { .index = MSG_NF_SIG_IDX, .value = 4.0 },
+            { .index = MSG_NF_ALIVE_IDX, .value = 1.0 },
+        };
+        simmock_print_scalar_signals(mock, LOG_DEBUG);
+        simmock_signal_check(
+            mock, NETWORK_NAME, s_checks, ARRAY_SIZE(s_checks), NULL);
+    }
+    /* 5.5-10ms - stable, no value change, no Tx*/
+    {
+        for (uint32_t i = 0; i < 9; i++) {
+            assert_int_equal(simmock_step(mock, true), 0);
+            assert_int_equal(network_model->sv_network->length[0] > 0,
+                false);  // can_bus has no data.
+            SignalCheck s_checks[] = {
+                { .index = MSG_NF_SIG_IDX, .value = 4.0 },
+                { .index = MSG_NF_ALIVE_IDX, .value = 1.0 },
+            };
+            simmock_print_scalar_signals(mock, LOG_DEBUG);
+            simmock_signal_check(
+                mock, NETWORK_NAME, s_checks, ARRAY_SIZE(s_checks), NULL);
+        }
+    }
+    /* 10.5ms - Set a signal value. */
+    {
+        mock->sv_signal->scalar[MSG_NF_SIG_IDX] = 6;
+        assert_int_equal(simmock_step(mock, true), 0);
+        assert_int_equal(network_model->sv_network->length[0] > 0,
+            true);  // can_bus has data.
+        SignalCheck s_checks[] = {
+            { .index = MSG_NF_SIG_IDX, .value = 6.0 },
+            { .index = MSG_NF_ALIVE_IDX, .value = 2.0 },
+        };
+        simmock_print_scalar_signals(mock, LOG_DEBUG);
+        simmock_signal_check(
+            mock, NETWORK_NAME, s_checks, ARRAY_SIZE(s_checks), NULL);
+    }
+    /* 10.5-15ms - stable, no value change, no Tx*/
+    {
+        for (uint32_t i = 0; i < 9; i++) {
+            assert_int_equal(simmock_step(mock, true), 0);
+            assert_int_equal(network_model->sv_network->length[0] > 0,
+                false);  // can_bus has no data.
+            SignalCheck s_checks[] = {
+                { .index = MSG_NF_SIG_IDX, .value = 6.0 },
+                { .index = MSG_NF_ALIVE_IDX, .value = 2.0 },
+            };
+            simmock_print_scalar_signals(mock, LOG_DEBUG);
+            simmock_signal_check(
+                mock, NETWORK_NAME, s_checks, ARRAY_SIZE(s_checks), NULL);
+        }
+    }
 }
 
 
@@ -162,6 +242,7 @@ int run_mstep_tests(void)
 
     const struct CMUnitTest tests[] = {
         cmocka_unit_test_setup_teardown(test_mstep, s, t),
+        cmocka_unit_test_setup_teardown(test_mstep_message_function, s, t),
     };
 
     return cmocka_run_group_tests_name("MSTEP", tests, NULL, NULL);