diff --git a/UnitTest/ActivityDiagramTests.cs b/UnitTest/ActivityDiagramTests.cs
index 84d1292dce15ca57cac1591881444d43739ed850..f83d7e0e0da0df41e87418177817222f8f623300 100644
--- a/UnitTest/ActivityDiagramTests.cs
+++ b/UnitTest/ActivityDiagramTests.cs
@@ -59,7 +59,7 @@ public class ActivityDiagramTests
         XmlDocument xmlDoc = new XmlDocument();
         xmlDoc.LoadXml(xmi);
         XmlNodeList nodes = xmlDoc.SelectNodes("//node[contains(@name, 'Activity')]");
-        Assert.IsTrue(nodes.Count == numberOfActivities,
+        Assert.That(nodes.Count == numberOfActivities,
             $"Number of activities added to XMI should be {numberOfActivities}");
         RemoveGeneratedFile();
     }
@@ -87,7 +87,7 @@ public class ActivityDiagramTests
             XmlDocument xmlDoc = new XmlDocument();
             xmlDoc.LoadXml(xmi);
             XmlNodeList nodes = xmlDoc.SelectNodes("//node[contains(@name, 'Decision')]");
-            Assert.IsTrue(nodes.Count == decisionCount * 2 - 1,
+            Assert.That(nodes.Count == decisionCount * 2 - 1,
                 $"Number of decisions added to XMI should be {decisionCount * 2 - 1}");
             RemoveGeneratedFile();
         }
@@ -165,15 +165,15 @@ public class ActivityDiagramTests
             XmlDocument xmlDoc = new XmlDocument();
             xmlDoc.LoadXml(xmi);
             XmlNodeList nodes = xmlDoc.SelectNodes("//node[contains(@name, 'Decision')]");
-            Assert.IsTrue(nodes.Count == decisionCount, $"Number of decisions added to XMI should be {decisionCount}");
+            Assert.That(nodes.Count == decisionCount, $"Number of decisions added to XMI should be {decisionCount}");
             //test if number of activitises added to xmi <node name="Activity
             nodes = xmlDoc.SelectNodes("//node[contains(@name, 'Activity')]");
-            Assert.IsTrue(nodes.Count == decisionCount * actionsCount,
+            Assert.That(nodes.Count == decisionCount * actionsCount,
                 $"Number of activities added to XMI should be {decisionCount * actionsCount}");
             if (addMerge)
             {
                 nodes = xmlDoc.SelectNodes("//node[contains(@name, 'Merge')]");
-                Assert.IsTrue(nodes.Count == decisionCount-1, $"Number of merges added to XMI should be {decisionCount}");
+                Assert.That(nodes.Count == decisionCount-1, $"Number of merges added to XMI should be {decisionCount}");
             }
 
             RemoveGeneratedFile();
@@ -233,12 +233,12 @@ public class ActivityDiagramTests
         XmlDocument xmlDoc = new XmlDocument();
         xmlDoc.LoadXml(xmi);
         XmlNodeList nodes = xmlDoc.SelectNodes("//node[contains(@name, 'Decision')]");
-        Assert.IsTrue(nodes.Count == 10, $"Number of decisions added to XMI should be 10");
+        Assert.That(nodes.Count == 10, $"Number of decisions added to XMI should be 10");
         //test if number of activitises added to xmi <node name="Activity
         nodes = xmlDoc.SelectNodes("//node[contains(@name, 'Activity')]");
-        Assert.IsTrue(nodes.Count == 100, $"Number of activities added to XMI should be 100");
+        Assert.That(nodes.Count == 100, $"Number of activities added to XMI should be 100");
         nodes = xmlDoc.SelectNodes("//node[contains(@name, 'Loop')]");
-        Assert.IsTrue(nodes.Count == 10, $"Number of loops added to XMI should be 10");
+        Assert.That(nodes.Count == 10, $"Number of loops added to XMI should be 10");
     }
 
     void ValidateSchema()
@@ -266,7 +266,7 @@ public class ActivityDiagramTests
         }
 
         // Assert that there are no errors
-        Assert.IsTrue(_errors.Count == 0, "There should be no errors in the XMI file");
+        Assert.That(_errors.Count == 0, "There should be no errors in the XMI file");
         foreach ((string severity, string message) in _errors)
         {
             Console.WriteLine($"{severity}: {message}");
@@ -284,7 +284,7 @@ public class ActivityDiagramTests
     private void AssertCommonAssertions(string xmi)
     {
         Assert.IsFalse(string.IsNullOrEmpty(xmi), "XMI should not be null or empty");
-        Assert.IsTrue(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
+        Assert.That(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
         // Add more assertions based on the expected structure of your XMI
 
         if (!string.IsNullOrEmpty(generatedFileName))
diff --git a/UnitTest/ClassDiagramTests.cs b/UnitTest/ClassDiagramTests.cs
index 9a75601215b20fac4360f5fad6320c9497dc1439..2d08224df7a59a90e75efc2743556da641290c62 100644
--- a/UnitTest/ClassDiagramTests.cs
+++ b/UnitTest/ClassDiagramTests.cs
@@ -32,7 +32,7 @@ public class ClassDiagramTests
         Assert.IsFalse(string.IsNullOrEmpty(xmi), "XMI should not be null or empty");
 
         // Additional assertions for XMI structure
-        Assert.IsTrue(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
+        Assert.That(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
         // Add more assertions based on the expected structure of your XMI
         
         File.WriteAllText(generatedFileName, xmi);
@@ -66,7 +66,7 @@ public class ClassDiagramTests
             Assert.IsFalse(string.IsNullOrEmpty(xmi), "XMI should not be null or empty");
 
             // Additional assertions for XMI structure
-            Assert.IsTrue(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
+            Assert.That(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
             // Add more assertions based on the expected structure of your XMI
         
             File.WriteAllText(generatedFileName, xmi);
@@ -93,7 +93,7 @@ public class ClassDiagramTests
             Assert.IsFalse(string.IsNullOrEmpty(xmi), "XMI should not be null or empty");
 
             // Additional assertions for XMI structure
-            Assert.IsTrue(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
+            Assert.That(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
             // Add more assertions based on the expected structure of your XMI
         
             File.WriteAllText(generatedFileName, xmi);
@@ -124,7 +124,7 @@ public class ClassDiagramTests
             Assert.IsFalse(string.IsNullOrEmpty(xmi), "XMI should not be null or empty");
 
             // Additional assertions for XMI structure
-            Assert.IsTrue(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
+            Assert.That(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
             // Add more assertions based on the expected structure of your XMI
         
             File.WriteAllText(generatedFileName, xmi);
@@ -269,7 +269,7 @@ public class ClassDiagramTests
             AssertCommonAssertions(xmi);
 
             // Add specific assertions for generalization
-            Assert.IsTrue(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
+            Assert.That(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
         }
         
         [Test]
@@ -286,7 +286,7 @@ public class ClassDiagramTests
             AssertCommonAssertions(xmi);
 
             // Add specific assertions for generalization
-            Assert.IsTrue(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
+            Assert.That(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
         }
         
         [Test]
@@ -304,7 +304,7 @@ public class ClassDiagramTests
             AssertCommonAssertions(xmi);
 
             // Add specific assertions for generalization
-            Assert.IsTrue(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
+            Assert.That(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
         }
         
         [Test]
@@ -322,7 +322,7 @@ public class ClassDiagramTests
             AssertCommonAssertions(xmi);
 
             // Add specific assertions for generalization
-            Assert.IsTrue(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
+            Assert.That(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
         }
         [Test]
         public void BuildDiagramWithGeneralizationAndAssociationAndOperationAndProperty()
@@ -340,7 +340,7 @@ public class ClassDiagramTests
             AssertCommonAssertions(xmi);
 
             // Add specific assertions for generalization
-            Assert.IsTrue(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
+            Assert.That(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
         }
         [Test]
         public void BuildDiagramWithGeneralizationAndAssociationAndOperationAndPropertyAndPackage()
@@ -366,7 +366,7 @@ public class ClassDiagramTests
             AssertCommonAssertions(xmi);
 
             // Add specific assertions for generalization
-            Assert.IsTrue(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
+            Assert.That(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
         }
         [Test]
         public void BuildDiagramWithGeneralizationAndAssociationAndOperationAndPropertyAndPackageAndMultipleClasses()
@@ -400,7 +400,7 @@ public class ClassDiagramTests
             AssertCommonAssertions(xmi);
 
             // Add specific assertions for generalization
-            Assert.IsTrue(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
+            Assert.That(xmi.Contains("general=\"TestPackage-Class1\""), "XMI should contain Generalization");
         }
 
         [Test]
@@ -470,7 +470,7 @@ public class ClassDiagramTests
         }
 
         // Assert that there are no errors
-        Assert.IsTrue(_errors.Count == 0, "There should be no errors in the XMI file");
+        Assert.That(_errors.Count == 0, "There should be no errors in the XMI file");
         foreach ((string severity, string message) in _errors)
         {
             Console.WriteLine($"{severity}: {message}");
@@ -488,7 +488,7 @@ public class ClassDiagramTests
     private void AssertCommonAssertions(string xmi)
     {
         Assert.IsFalse(string.IsNullOrEmpty(xmi), "XMI should not be null or empty");
-        Assert.IsTrue(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
+        Assert.That(xmi.Contains("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"), "XMI should contain the XML header");
         // Add more assertions based on the expected structure of your XMI
 
         if (!string.IsNullOrEmpty(generatedFileName))
diff --git a/UnitTest/WebApiTests.cs b/UnitTest/WebApiTests.cs
index 8394d02b9ead18e703f7b9eb9e488745bb30073c..78aabc1675aa3394747d12a6262c828fc2fe0eaa 100644
--- a/UnitTest/WebApiTests.cs
+++ b/UnitTest/WebApiTests.cs
@@ -1,6 +1,7 @@
 using System.Text;
 using Database;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.Logging;
 using Newtonsoft.Json;
 using WebAPI.Controllers;
 using WebAPI.DTO;
@@ -41,6 +42,7 @@ public class WebApiTests
     public void AuthenticationTest(string username = "TestUser", string password = "TestPassword")
     {
         var path = Path.Join(Directory.GetCurrentDirectory(), "users.json");
+        //create logger
         ApiController apiController = new ApiController(null, null, path);
         var model = new AuthenticateUserModel()
         {
@@ -49,13 +51,13 @@ public class WebApiTests
         };
         var result = apiController.AuthenticateUserPassword(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is OkObjectResult);
+        Assert.That(result is OkObjectResult);
         var okResult = result as OkObjectResult;
         var token = okResult.Value as string;
-        Assert.IsTrue(!string.IsNullOrEmpty(token));
+        Assert.That(!string.IsNullOrEmpty(token));
     }
     
-    public string TestUserAuthenticationProcedure(string username = "TestUser", string password = "TestPassword")
+    private string TestUserAuthenticationProcedure(string username = "TestUser", string password = "TestPassword")
     {
         var path = Path.Join(Directory.GetCurrentDirectory(), "users.json");
         ApiController apiController = new ApiController(null, null, path);
@@ -66,10 +68,10 @@ public class WebApiTests
         };
         var result = apiController.AuthenticateUserPassword(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is OkObjectResult);
+        Assert.That(result is OkObjectResult);
         var okResult = result as OkObjectResult;
         var token = okResult.Value as string;
-        Assert.IsTrue(!string.IsNullOrEmpty(token));
+        Assert.That(!string.IsNullOrEmpty(token));
         return okResult.Value as string;
     }
     
@@ -85,7 +87,7 @@ public class WebApiTests
         };
         var result = apiController.AuthenticateUserPassword(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is BadRequestObjectResult);
+        Assert.That(result is BadRequestObjectResult);
     }
     
     [Test]
@@ -100,7 +102,7 @@ public class WebApiTests
         };
         var result = apiController.AuthenticateUserPassword(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is NotFoundObjectResult);
+        Assert.That(result is NotFoundObjectResult);
     }
     
     [Test]
@@ -115,7 +117,7 @@ public class WebApiTests
         };
         var result = apiController.AuthenticateUserPassword(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is NotFoundObjectResult);
+        Assert.That(result is NotFoundObjectResult);
     }
     
     [Test]
@@ -130,7 +132,7 @@ public class WebApiTests
         };
         var result = apiController.AuthenticateUserPassword(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is BadRequestObjectResult);
+        Assert.That(result is BadRequestObjectResult);
     }
     
     [Test]
@@ -145,7 +147,7 @@ public class WebApiTests
         };
         var result = apiController.AuthenticateUserPassword(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is NotFoundObjectResult);
+        Assert.That(result is NotFoundObjectResult);
     }
     #endregion
 
@@ -165,10 +167,10 @@ public class WebApiTests
         };
         var result = apiController.RegisterUser(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is OkObjectResult);
+        Assert.That(result is OkObjectResult);
         var okResult = result as OkObjectResult;
-        Assert.IsTrue(!string.IsNullOrEmpty(okResult.Value as string));
-        Assert.IsTrue((okResult.Value as string) == "User created");
+        Assert.That(!string.IsNullOrEmpty(okResult.Value as string));
+        Assert.That((okResult.Value as string) == "User created");
     }
     
     [Test]
@@ -185,10 +187,10 @@ public class WebApiTests
         };
         var result = apiController.RegisterUser(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is BadRequestObjectResult);
+        Assert.That(result is BadRequestObjectResult);
         var okResult = result as BadRequestObjectResult;
-        Assert.IsTrue(!string.IsNullOrEmpty(okResult.Value as string));
-        Assert.IsTrue((okResult.Value as string) == "User already exists");
+        Assert.That(!string.IsNullOrEmpty(okResult.Value as string));
+        Assert.That((okResult.Value as string) == "User already exists");
     }
     
     [Test]
@@ -204,10 +206,10 @@ public class WebApiTests
         };
         var result = apiController.RegisterUser(model);
         //assert that returns Ok and parse token
-        Assert.IsTrue(result is BadRequestObjectResult);
+        Assert.That(result is BadRequestObjectResult);
         var okResult = result as BadRequestObjectResult;
-        Assert.IsTrue(!string.IsNullOrEmpty(okResult.Value as string));
-        Assert.IsTrue((okResult.Value as string) == "Invalid token");
+        Assert.That(!string.IsNullOrEmpty(okResult.Value as string));
+        Assert.That((okResult.Value as string) == "Invalid token");
     }
 
     [Test]
@@ -237,18 +239,18 @@ public class WebApiTests
 
         if (getValidToken)
         {
-            Assert.IsTrue(result is OkObjectResult);
+            Assert.That(result is OkObjectResult);
             var okResult = result as OkObjectResult;
-            Assert.IsTrue(okResult.Value is List<SourceCodeExt>);
+            Assert.That(okResult.Value is List<SourceCodeExt>);
             var list = okResult.Value as List<SourceCodeExt>;
-            Assert.IsTrue(list.Count == count);
+            Assert.That(list.Count == count);
         }
         else
         {
-            Assert.IsTrue(result is BadRequestObjectResult);
+            Assert.That(result is BadRequestObjectResult);
             var okResult = result as BadRequestObjectResult;
-            Assert.IsTrue(okResult.Value is string);
-            Assert.IsTrue(okResult.Value as string == "Invalid token");
+            Assert.That(okResult.Value is string);
+            Assert.That(okResult.Value as string == "Invalid token");
         }
         
     }
@@ -278,15 +280,15 @@ public class WebApiTests
         var result = apiController.UploadCode(model);
         if (getValidToken)
         {
-            Assert.IsTrue(result is OkObjectResult);
+            Assert.That(result is OkObjectResult);
             var okResult = result as OkObjectResult;
-            Assert.IsTrue(okResult.Value is string);
+            Assert.That(okResult.Value is string);
             //parse Code uploaded, id: 1
             var value = okResult.Value as string;
             var id = value.Split("Code uploaded, id:")[1].Trim();
-            Assert.IsTrue(!string.IsNullOrEmpty(id));
-            Assert.IsTrue(int.TryParse(id, out int idInt));
-            Assert.IsTrue(idInt == 1);
+            Assert.That(!string.IsNullOrEmpty(id));
+            Assert.That(int.TryParse(id, out int idInt));
+            Assert.That(idInt == 1);
             ListAll(true, 1);
             ListOne(true, 1, true);
             ConvertToActivityDiagram(true, 1, true);
@@ -297,10 +299,10 @@ public class WebApiTests
         }
         else
         {
-            Assert.IsTrue(result is BadRequestObjectResult);
+            Assert.That(result is BadRequestObjectResult);
             var okResult = result as BadRequestObjectResult;
-            Assert.IsTrue(okResult.Value is string);
-            Assert.IsTrue(okResult.Value as string == "Invalid token");
+            Assert.That(okResult.Value is string);
+            Assert.That(okResult.Value as string == "Invalid token");
         }
     }
     
@@ -324,27 +326,27 @@ public class WebApiTests
         {
             if (codeExists)
             {
-                Assert.IsTrue(result is OkObjectResult);
+                Assert.That(result is OkObjectResult);
                 var okResult = result as OkObjectResult;
-                Assert.IsTrue(okResult.Value is SourceCodeExt);
+                Assert.That(okResult.Value is SourceCodeExt);
                 var code = okResult.Value as SourceCodeExt;
-                Assert.IsTrue(code.Id == id);
+                Assert.That(code.Id == id);
             }
             else
             {
-                Assert.IsTrue(result is NotFoundObjectResult);
+                Assert.That(result is NotFoundObjectResult);
                 var okResult = result as NotFoundObjectResult;
-                Assert.IsTrue(okResult.Value is string);
-                Assert.IsTrue(okResult.Value as string == "Code does not exist");
+                Assert.That(okResult.Value is string);
+                Assert.That(okResult.Value as string == "Code does not exist");
             }
             
         }
         else
         {
-            Assert.IsTrue(result is BadRequestObjectResult);
+            Assert.That(result is BadRequestObjectResult);
             var okResult = result as BadRequestObjectResult;
-            Assert.IsTrue(okResult.Value is string);
-            Assert.IsTrue(okResult.Value as string == "Invalid token");
+            Assert.That(okResult.Value is string);
+            Assert.That(okResult.Value as string == "Invalid token");
         }
     }
     #endregion
@@ -370,30 +372,30 @@ public class WebApiTests
         {
             if (codeExists)
             {
-                Assert.IsTrue(result is FileStreamResult);
+                Assert.That(result is FileStreamResult);
                 var fileStreamResult = result as FileStreamResult;
-                Assert.IsTrue(fileStreamResult.ContentType == "application/xml");
-                Assert.IsTrue(!string.IsNullOrEmpty(fileStreamResult.FileDownloadName));
+                Assert.That(fileStreamResult.ContentType == "application/xml");
+                Assert.That(!string.IsNullOrEmpty(fileStreamResult.FileDownloadName));
                 
                 //check if filestream is not empty
                 var stream = fileStreamResult.FileStream;
-                Assert.IsTrue(stream.Length > 0);
+                Assert.That(stream.Length > 0);
             }
             else
             {
-                Assert.IsTrue(result is NotFoundObjectResult);
+                Assert.That(result is NotFoundObjectResult);
                 var okResult = result as NotFoundObjectResult;
-                Assert.IsTrue(okResult.Value is string);
-                Assert.IsTrue(okResult.Value as string == "Code does not exist");
+                Assert.That(okResult.Value is string);
+                Assert.That(okResult.Value as string == "Code does not exist");
             }
             
         }
         else
         {
-            Assert.IsTrue(result is BadRequestObjectResult);
+            Assert.That(result is BadRequestObjectResult);
             var okResult = result as BadRequestObjectResult;
-            Assert.IsTrue(okResult.Value is string);
-            Assert.IsTrue(okResult.Value as string == "Invalid token");
+            Assert.That(okResult.Value is string);
+            Assert.That(okResult.Value as string == "Invalid token");
         }
     }
     
@@ -418,30 +420,30 @@ public class WebApiTests
         {
             if (codeExists)
             {
-                Assert.IsTrue(result is FileStreamResult);
+                Assert.That(result is FileStreamResult);
                 var fileStreamResult = result as FileStreamResult;
-                Assert.IsTrue(fileStreamResult.ContentType == "application/xml");
-                Assert.IsTrue(!string.IsNullOrEmpty(fileStreamResult.FileDownloadName));
+                Assert.That(fileStreamResult.ContentType == "application/xml");
+                Assert.That(!string.IsNullOrEmpty(fileStreamResult.FileDownloadName));
                 
                 //check if filestream is not empty
                 var stream = fileStreamResult.FileStream;
-                Assert.IsTrue(stream.Length > 0);
+                Assert.That(stream.Length > 0);
             }
             else
             {
-                Assert.IsTrue(result is NotFoundObjectResult);
+                Assert.That(result is NotFoundObjectResult);
                 var okResult = result as NotFoundObjectResult;
-                Assert.IsTrue(okResult.Value is string);
-                Assert.IsTrue(okResult.Value as string == "Code does not exist");
+                Assert.That(okResult.Value is string);
+                Assert.That(okResult.Value as string == "Code does not exist");
             }
             
         }
         else
         {
-            Assert.IsTrue(result is BadRequestObjectResult);
+            Assert.That(result is BadRequestObjectResult);
             var okResult = result as BadRequestObjectResult;
-            Assert.IsTrue(okResult.Value is string);
-            Assert.IsTrue(okResult.Value as string == "Invalid token");
+            Assert.That(okResult.Value is string);
+            Assert.That(okResult.Value as string == "Invalid token");
         }
     }
 
@@ -474,26 +476,26 @@ public class WebApiTests
         {
             if (codeExists)
             {
-                Assert.IsTrue(result is OkObjectResult);
+                Assert.That(result is OkObjectResult);
                 var okResult = result as OkObjectResult;
-                Assert.IsTrue(okResult.Value is string);
-                Assert.IsTrue(okResult.Value as string == "Code removed");
+                Assert.That(okResult.Value is string);
+                Assert.That(okResult.Value as string == "Code removed");
             }
             else
             {
-                Assert.IsTrue(result is NotFoundObjectResult);
+                Assert.That(result is NotFoundObjectResult);
                 var okResult = result as NotFoundObjectResult;
-                Assert.IsTrue(okResult.Value is string);
-                Assert.IsTrue(okResult.Value as string == "Code does not exist");
+                Assert.That(okResult.Value is string);
+                Assert.That(okResult.Value as string == "Code does not exist");
             }
             
         }
         else
         {
-            Assert.IsTrue(result is BadRequestObjectResult);
+            Assert.That(result is BadRequestObjectResult);
             var okResult = result as BadRequestObjectResult;
-            Assert.IsTrue(okResult.Value is string);
-            Assert.IsTrue(okResult.Value as string == "Invalid token");
+            Assert.That(okResult.Value is string);
+            Assert.That(okResult.Value as string == "Invalid token");
         }
     }
     #endregion
diff --git a/WebAPI/Controllers/ApiController.cs b/WebAPI/Controllers/ApiController.cs
index 2fb592c841b35b4902a225049c47c33768011841..4117177e9d6561cd1a0422c8295785df3cfcfc9c 100644
--- a/WebAPI/Controllers/ApiController.cs
+++ b/WebAPI/Controllers/ApiController.cs
@@ -19,11 +19,11 @@ namespace WebAPI.Controllers
     [Route("api/")]
     public class ApiController : ControllerBase
     {
-        private readonly ILogger<ApiController> _logger;
-        private readonly IConfiguration _configuration;
+        private readonly ILogger<ApiController>? _logger;
+        private readonly IConfiguration? _configuration;
         private int tokenValidityMinutes => _configuration?.GetValue<int>("UserManagement:TokenValidityMinutes") ?? 30;
 
-        public ApiController(ILogger<ApiController> logger, IConfiguration configuration, string dbPath = "default-users.json")
+        public ApiController(ILogger<ApiController>? logger, IConfiguration? configuration, string dbPath = "default-users.json")
         {
             _logger = logger;
             _configuration = configuration;