diff --git a/tests/modbus_server_tester.hpp b/tests/modbus_server_tester.hpp
index 79955a0..c9b4416 100644
--- a/tests/modbus_server_tester.hpp
+++ b/tests/modbus_server_tester.hpp
@@ -14,6 +14,7 @@
     friend class ServerTester;
 };
 
+// Read Holding Registers Testing Constants
 static constexpr uint8_t testDeviceAddress = 0xa;
 constexpr uint16_t testSuccessReadHoldingRegisterOffset = 0x0102;
 constexpr uint16_t testSuccessReadHoldingRegisterCount = 0x2;
@@ -22,6 +23,14 @@
     testSuccessReadHoldingRegisterResponse = {0x1234, 0x5678};
 constexpr uint16_t testFailureReadHoldingRegister = 0x0105;
 
+// Device Inventory Testing Constants
+constexpr uint16_t testReadHoldingRegisterModelOffset = 0x0112;
+constexpr uint16_t testReadHoldingRegisterModelCount = 0x8;
+constexpr std::array<uint16_t, testReadHoldingRegisterModelCount>
+    testReadHoldingRegisterModel = {0x5244, 0x4630, 0x3430, 0x4453,
+                                    0x5335, 0x3139, 0x0000, 0x3000};
+constexpr std::string testReadHoldingRegisterModelStr = "RDF040DSS519";
+
 class ServerTester
 {
   public:
@@ -39,5 +48,6 @@
 
     int fd;
     sdbusplus::async::fdio fdioInstance;
+    sdbusplus::async::mutex mutex;
 };
 } // namespace phosphor::modbus::test