New unit test with invalid slave and invalid request

src/modbus.c

@@ -250,7 +250,8 @@ static uint8_t compute_meta_length_after_function(int function,
 }
 
 /* Computes the length to read after the meta information (address, count, etc) */
-static int compute_data_length_after_meta(modbus_t *ctx, uint8_t *msg, msg_type_t msg_type)
+static int compute_data_length_after_meta(modbus_t *ctx, uint8_t *msg,
+                                          msg_type_t msg_type)
 {
     int function = msg[ctx->backend->header_length];
     int length;

tests/unit-test-client.c

@@ -300,7 +300,8 @@ int main(int argc, char *argv[])
 
     /** INPUT REGISTERS **/
     rc = modbus_read_input_registers(ctx, UT_INPUT_REGISTERS_ADDRESS,
-                                     UT_INPUT_REGISTERS_NB, tab_rp_registers);
+                                     UT_INPUT_REGISTERS_NB,
+                                     tab_rp_registers);
     printf("1/1 modbus_read_input_registers: ");
     if (rc != UT_INPUT_REGISTERS_NB) {
         printf("FAILED (nb points %d)\n", rc);
@@ -377,7 +378,8 @@ int main(int argc, char *argv[])
     }
 
     rc = modbus_read_input_registers(ctx, UT_INPUT_REGISTERS_ADDRESS,
-                                     UT_INPUT_REGISTERS_NB + 1, tab_rp_registers);
+                                     UT_INPUT_REGISTERS_NB + 1,
+                                     tab_rp_registers);
     printf("* modbus_read_input_registers: ");
     if (rc == -1 && errno == EMBXILADD)
         printf("OK\n");
@@ -484,12 +486,17 @@ int main(int argc, char *argv[])
 
     /** SLAVE REPLY **/
     printf("\nTEST SLAVE REPLY:\n");
-    modbus_set_slave(ctx, 18);
+    modbus_set_slave(ctx, INVALID_SERVER_ID);
     rc = modbus_read_registers(ctx, UT_REGISTERS_ADDRESS,
                                UT_REGISTERS_NB, tab_rp_registers);
     if (use_backend == RTU) {
+        const int RAW_REQ_LENGTH = 6;
+        uint8_t raw_req[] = { INVALID_SERVER_ID, 0x03, 0x00, 0x01, 0xFF, 0xFF };
+        int req_length;
+        uint8_t rsp[MODBUS_TCP_MAX_ADU_LENGTH];
+
         /* No response in RTU mode */
-        printf("1/4 No response from slave %d: ", 18);
+        printf("1/4-A No response from slave %d: ", INVALID_SERVER_ID);
 
         if (rc == -1 && errno == ETIMEDOUT) {
             printf("OK\n");
@@ -497,6 +504,23 @@ int main(int argc, char *argv[])
             printf("FAILED\n");
             goto close;
         }
+
+        /* Send an invalid query with a wrong slave ID */
+        req_length = modbus_send_raw_request(
+            ctx, raw_req,
+            RAW_REQ_LENGTH * sizeof(uint8_t));
+        rc = modbus_receive_confirmation(ctx, rsp);
+
+        printf("1/4-B No response from slave %d with invalid request: ",
+               INVALID_SERVER_ID);
+
+        if (rc == -1 && errno == ETIMEDOUT) {
+            printf("OK\n");
+        } else {
+            printf("FAILED (%d)\n", rc);
+            goto close;
+        }
+
     } else {
         /* Response in TCP mode */
         printf("1/4 Response from slave %d: ", 18);

tests/unit-test.h

@@ -31,7 +31,8 @@
 # endif
 #endif
 
-#define SERVER_ID 17
+#define SERVER_ID         17
+#define INVALID_SERVER_ID 18
 
 const uint16_t UT_BITS_ADDRESS = 0x13;
 const uint16_t UT_BITS_NB = 0x25;