feat(reply-delay): Add getter to read reply delay

Also added valid tests

Signed-off-by: Bobo Bäck Engström <bobo@id8-engineering.io>

Author: Dexter9532

src/em511/em511.py

@@ -33,6 +33,8 @@ class Em511:
     PARITY_MAX_VALUE = 2
     STOP_BIT_MIN_VALUE = 1
     STOP_BIT_MAX_VALUE = 2
+    REPLY_DELAY_MIN_VALUE = 0
+    REPLY_DELAY_MAX_VALUE = 1000
 
     EM511_REGISTER_V = 0x0
     EM511_REGISTER_A = 0x2
@@ -48,6 +50,7 @@ class Em511:
     EM511_REGISTER_BAUD_RATE = 0x2001
     EM511_REGISTER_PARITY = 0x2002
     EM511_REGISTER_STOP_BIT = 0x2003
+    EM511_REGISTER_REPLY_DELAY = 0x2004
 
     SCALE_10 = 10
     SCALE_100 = 100
@@ -379,6 +382,27 @@ def stop_bit(self) -> int:
             raise ValueError(msg)
         return value
 
+    @property
+    def reply_delay(self) -> int:
+        """Reply delay.
+
+        Range: 0-1000 ms (default=0)
+
+        Returns:
+            int: Current reply delay value.
+
+        Raises:
+            ValueError: If input is at max value or above.
+            ValueError: If reply delay is out of range.
+            ModbusException: If failed to read input register.
+        """
+        regs = self._read_input_registers(self.EM511_REGISTER_REPLY_DELAY, self.INT16_REG_COUNT)
+        value = self._unpack(regs, self.EM511_REGISTER_REPLY_DELAY)
+        if not (self.REPLY_DELAY_MIN_VALUE <= value <= self.REPLY_DELAY_MAX_VALUE):
+            msg = f"Invalid reply delay value: {value}. Must be between 0 and 1000."
+            raise ValueError(msg)
+        return value
+
     @password.setter
     def password(self, value: int) -> None:
         """Password.

src/em511/test_em511.py

@@ -476,6 +476,44 @@ def test_get_stop_bit() -> None:
         _ = meter.stop_bit
 
 
+def test_get_reply_delay() -> None:
+    """Test Get reply delay."""
+    client = MagicMock()
+    mock_result = MagicMock()
+    mock_result.isError.return_value = False
+    meter = Em511(1, client)
+
+    """Test 1: should pass"""
+    mock_result.registers = [0x3E8]
+    client.read_input_registers.return_value = mock_result
+    value = meter.reply_delay
+    assert value == 1000
+
+    """Test 2: Should pass."""
+    mock_result.registers = [0x0]
+    client.read_input_registers.return_value = mock_result
+    value = meter.reply_delay
+    assert value == 0
+
+    """Test 3: Should raise exception due to value not in range"""
+    mock_result.registers = [0x3E9]
+    client.read_input_registers.return_value = mock_result
+    with pytest.raises(ValueError, match="Invalid reply delay value:"):
+        _ = meter.reply_delay
+
+    """Test 4: Should raise exception due to more registers in use than allowed."""
+    mock_result.registers = [0x1860, 0x0023, 0x5743]
+    client.read_input_registers.return_value = mock_result
+    with pytest.raises(ValueError, match="Unexpected register count:"):
+        _ = meter.reply_delay
+
+    """Test 5: Should raise exception if input value exceeds maximum value, display shows 'EEE', 16-bit register."""
+    mock_result.registers = [0x7FFF]
+    client.read_input_registers.return_value = mock_result
+    with pytest.raises(ValueError, match="Input overflow EEE for 16-bit register: "):
+        _ = meter.reply_delay
+
+
 def test_set_password() -> None:
     """Test Set Password."""
     client = MagicMock()