### Commit Summary

- **TestSetup.cs**
  - Updated `CreateTestConfig` method to initialize `Config` with required properties using object initializer syntax.

- **ProxyIntegrationTests.cs**
  - Added null checks for `mockServer.Urls` before accessing it to prevent potential null reference exceptions.
  - Improved error handling for mock server URL access.

- **VRChatAuthenticationTests.cs**
  - Added null checks for `mockServer.Urls` before accessing it to prevent potential null reference exceptions.
  - Enhanced the mock server setup to include null checks for request body content.

- **Config.cs**
  - Added the `required` modifier to non-nullable properties in `ConfigAccount` and `iConfig` classes.
  - Updated the `Load` method to initialize the `Config` instance with required properties using object initializer syntax.

- **Program.cs**
  - Added a null check for `result.CloseStatus` in WebSocket handling to prevent potential null reference exceptions.

Tests/Helpers/TestSetup.cs

@@ -23,23 +23,23 @@ namespace VRCAuthProxy.Tests.Helpers
         /// </summary>
         public static Config CreateTestConfig()
         {
-            var config = new Config();
-            config.Accounts = new List<ConfigAccount>
+            return new Config
             {
-                new ConfigAccount
+                Accounts = new List<ConfigAccount>
                 {
-                    username = "testuser1",
-                    password = "testpassword1",
-                    totpSecret = "TESTSECRET1"
-                },
-                new ConfigAccount
-                {
-                    username = "testuser2",
-                    password = "testpassword2"
+                    new ConfigAccount
+                    {
+                        username = "testuser1",
+                        password = "testpassword1",
+                        totpSecret = "TESTSECRET1"
+                    },
+                    new ConfigAccount
+                    {
+                        username = "testuser2",
+                        password = "testpassword2"
+                    }
                 }
             };
-            
-            return config;
         }
     }
 }