diff --git a/test/user_mgr_test.cpp b/test/user_mgr_test.cpp
index 15a56fc..588c2fa 100644
--- a/test/user_mgr_test.cpp
+++ b/test/user_mgr_test.cpp
@@ -331,5 +331,34 @@
         sdbusplus::xyz::openbmc_project::User::Common::Error::UserNameExists);
 }
 
+TEST_F(
+    UserMgrInTest,
+    ThrowForUserNameConstraintsExceedIpmiMaxUserNameLenThrowsUserNameGroupFail)
+{
+    std::string strWith17Chars(17, 'A');
+    EXPECT_THROW(throwForUserNameConstraints(strWith17Chars, {"ipmi"}),
+                 sdbusplus::xyz::openbmc_project::User::Common::Error::
+                     UserNameGroupFail);
+}
+
+TEST_F(
+    UserMgrInTest,
+    ThrowForUserNameConstraintsExceedSystemMaxUserNameLenThrowsInvalidArgument)
+{
+    std::string strWith31Chars(31, 'A');
+    EXPECT_THROW(
+        throwForUserNameConstraints(strWith31Chars, {}),
+        sdbusplus::xyz::openbmc_project::Common::Error::InvalidArgument);
+}
+
+TEST_F(UserMgrInTest,
+       ThrowForUserNameConstraintsRegexMismatchThrowsInvalidArgument)
+{
+    std::string startWithNumber = "0ABC";
+    EXPECT_THROW(
+        throwForUserNameConstraints(startWithNumber, {"ipmi"}),
+        sdbusplus::xyz::openbmc_project::Common::Error::InvalidArgument);
+}
+
 } // namespace user
 } // namespace phosphor
diff --git a/user_mgr.hpp b/user_mgr.hpp
index dd73fff..d298bf0 100644
--- a/user_mgr.hpp
+++ b/user_mgr.hpp
@@ -246,6 +246,16 @@
      */
     void throwForUserExists(const std::string& userName);
 
+    /** @brief check user name constraints
+     *  method to check user name constraints and throw if failed.
+     *
+     *  @param[in] userName - name of the user
+     *  @param[in] groupNames - user groups
+     */
+    void
+        throwForUserNameConstraints(const std::string& userName,
+                                    const std::vector<std::string>& groupNames);
+
   private:
     /** @brief sdbusplus handler */
     sdbusplus::bus_t& bus;
@@ -281,16 +291,6 @@
      */
     UserSSHLists getUserAndSshGrpList(void);
 
-    /** @brief check user name constraints
-     *  method to check user name constraints and throw if failed.
-     *
-     *  @param[in] userName - name of the user
-     *  @param[in] groupNames - user groups
-     */
-    void
-        throwForUserNameConstraints(const std::string& userName,
-                                    const std::vector<std::string>& groupNames);
-
     /** @brief check group user count
      *  method to check max group user count, and throw if limit reached
      *