diff --git a/tests/holding_register_test.py b/tests/holding_register_test.py
deleted file mode 100755
index 335669f..0000000
--- a/tests/holding_register_test.py
+++ /dev/null
@@ -1,49 +0,0 @@
-#!/usr/bin/env python3
-from time import sleep
-import minimalmodbus
-import serial
-
-slave_address = 254
-instrument = minimalmodbus.Instrument('/dev/ttyUSB0', slave_address, close_port_after_each_call=True)  # port name, slave address (in decimal)
-
-instrument.serial.baudrate = 19200
-instrument.serial.bytesize = 8
-instrument.serial.parity   = serial.PARITY_EVEN
-instrument.serial.stopbits = 1
-instrument.serial.timeout  = 0.05          # seconds
-instrument.mode = minimalmodbus.MODE_RTU   # rtu or ascii mode
-instrument.clear_buffers_before_each_transaction = True
-
-# holding register numbers
-LED_on_register = 0
-LED_brightness_register = 1
-LED_smooth_register = 2
-CO2_alert_limit_1_register = 3
-CO2_alert_limit_2_register = 4
-SCD4x_temperature_offset_register = 5
-MODBUS_address_register = 6
-baudrate_register = 7
-# holding register readout
-print('---- Reading from holding registers ----')
-#LED_on = int(instrument.read_register(LED_on_register, 1, functioncode=3) * 10)
-#LED_brightness = int(instrument.read_register(LED_brightness_register, 1, functioncode=3) * 10)
-#LED_smooth = int(instrument.read_register(LED_smooth_register, 1, functioncode=3) * 10)
-#CO2_alert_limit_1 = int(instrument.read_register(CO2_alert_limit_1_register, 1, functioncode=3) * 10)
-#CO2_alert_limit_2 = int(instrument.read_register(CO2_alert_limit_2_register, 1, functioncode=3) * 10)
-#SCD4x_temperature_offset = int(instrument.read_register(SCD4x_temperature_offset_register, 1, functioncode=3) * 10)
-#MODBUS_address = int(instrument.read_register(MODBUS_address_register, 1, functioncode=3) * 10)
-#baudrate = int(instrument.read_register(baudrate_register, 1, functioncode=3) * 10)
-# print
-#print(
-#f'''LED_on = {LED_on}
-#LED_brightness = {LED_brightness}
-#LED_smooth = {LED_smooth}
-#CO2_alert_limit_1 = {CO2_alert_limit_1}
-#CO2_alert_limit_2 = {CO2_alert_limit_2}
-#SCD4x_temperature_offset = {SCD4x_temperature_offset}
-#MODBUS_address = {MODBUS_address}
-#baudrate = {baudrate}
-#''')
-# write to holding register
-print('---- Writing to holding registers ----')
-instrument.write_register(LED_on_register, 0, functioncode=6)
diff --git a/tests/minimalmodbus_test.py b/tests/read_input_register_test.py
similarity index 94%
rename from tests/minimalmodbus_test.py
rename to tests/read_input_register_test.py
index 999ae00..e1067c5 100755
--- a/tests/minimalmodbus_test.py
+++ b/tests/read_input_register_test.py
@@ -1,5 +1,6 @@
 #!/usr/bin/env python3
 from time import sleep
+from sys import exit
 import minimalmodbus
 import serial
 
@@ -14,6 +15,7 @@ instrument.serial.timeout  = 0.05          # seconds
 instrument.mode = minimalmodbus.MODE_RTU   # rtu or ascii mode
 instrument.clear_buffers_before_each_transaction = True
 
+print('---- Reading from input registers ----')
 # read
 CO2_addr = 9
 CO2 = instrument.read_register(CO2_addr, 1, functioncode=4) * 10
@@ -36,3 +38,5 @@ print(f'[{T_SCD4x_addr+30001}] T_SCD4x:\t{T_SCD4x} deg C')
 print(f'[{RH_SCD4x_addr+30001}] RH_SCD4x:\t{RH_SCD4x} %')
 print(f'[{T_SHT4x_signed_addr+30001}] T_SHT4x_signed:\t{T_SHT4x_signed} deg C')
 print(f'[{T_SCD4x_signed_addr+30001}] T_SCD4x_signed:\t{T_SCD4x_signed} deg C')
+print('---- DONE ----')
+exit(0)
diff --git a/tests/read_write_holding_registers_test.py b/tests/read_write_holding_registers_test.py
new file mode 100755
index 0000000..8225a71
--- /dev/null
+++ b/tests/read_write_holding_registers_test.py
@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+from time import sleep
+from sys import exit
+import minimalmodbus
+import serial
+
+slave_address = 254
+instrument = minimalmodbus.Instrument('/dev/ttyUSB0', slave_address, close_port_after_each_call=True)  # port name, slave address (in decimal)
+
+instrument.serial.baudrate = 19200
+instrument.serial.bytesize = 8
+instrument.serial.parity   = serial.PARITY_EVEN
+instrument.serial.stopbits = 1
+instrument.serial.timeout  = 0.05          # seconds
+instrument.mode = minimalmodbus.MODE_RTU   # rtu or ascii mode
+instrument.clear_buffers_before_each_transaction = True
+
+# holding register numbers
+LED_on_register = 0
+LED_brightness_register = 1
+LED_smooth_register = 2
+CO2_alert_limit_1_register = 3
+CO2_alert_limit_2_register = 4
+SCD4x_temperature_offset_register = 5
+MODBUS_address_register = 6
+baudrate_register = 7
+# holding register readout
+print('---- Reading from holding registers ----')
+LED_on = int(instrument.read_register(LED_on_register, 1, functioncode=3) * 10)
+LED_brightness = int(instrument.read_register(LED_brightness_register, 1, functioncode=3) * 10)
+LED_smooth = int(instrument.read_register(LED_smooth_register, 1, functioncode=3) * 10)
+CO2_alert_limit_1 = int(instrument.read_register(CO2_alert_limit_1_register, 1, functioncode=3) * 10)
+CO2_alert_limit_2 = int(instrument.read_register(CO2_alert_limit_2_register, 1, functioncode=3) * 10)
+SCD4x_temperature_offset = int(instrument.read_register(SCD4x_temperature_offset_register, 1, functioncode=3) * 10)
+MODBUS_address = int(instrument.read_register(MODBUS_address_register, 1, functioncode=3) * 10)
+baudrate = int(instrument.read_register(baudrate_register, 1, functioncode=3) * 10)
+# print
+reg_base = 40001
+print(
+f'''[{LED_on_register+reg_base}] LED_on = {LED_on}
+[{LED_brightness_register+reg_base}] LED_brightness = {LED_brightness}
+[{LED_smooth_register+reg_base}] LED_smooth = {LED_smooth}
+[{CO2_alert_limit_1_register+reg_base}] CO2_alert_limit_1 = {CO2_alert_limit_1}
+[{CO2_alert_limit_2_register+reg_base}] CO2_alert_limit_2 = {CO2_alert_limit_2}
+[{SCD4x_temperature_offset_register+reg_base}] SCD4x_temperature_offset = {SCD4x_temperature_offset}
+[{MODBUS_address_register+reg_base}] MODBUS_address = {MODBUS_address}
+[{baudrate_register+reg_base}] baudrate = {baudrate}''')
+# write to holding register
+print('---- Writing to holding registers ----')
+instrument.write_register(LED_on_register, 1, functioncode=6)
+print('---- DONE ----')
+exit(0)