Added tests

Application/PlayLists/Handlers/GetPlayListByIdQueryHandler.cs

@@ -14,10 +14,13 @@ namespace Musify.Application.PlayLists.Handlers
         {
             var playList = await database.PlayLists
                 .AsNoTracking()
+                .Where(p => p.Id == request.Id)
                 .Select(p => PlayListApplicationResponse.FromEntity(p))
-                .SingleOrDefaultAsync(p => p.Id == request.Id, cancellationToken);
+                .SingleOrDefaultAsync(cancellationToken);
 
-            return playList ?? Result<PlayListApplicationResponse>.NotFound();
+            return playList is null
+                ? Result<PlayListApplicationResponse>.NotFound()
+                : Result.Success(playList);
         }
     }
 }

Application/Tracks/Handlers/GetTrackByIdQueryHandler.cs

@@ -13,10 +13,13 @@ namespace Musify.Application.Tracks.Handlers
         public async ValueTask<Result<TrackApplicationResponse>> Handle(GetTrackByIdQuery request, CancellationToken cancellationToken)
         {
             var track = await database.Tracks.AsNoTracking()
+                .Where(t => t.Id == request.TrackId)
                 .Select(t => TrackApplicationResponse.FromEntity(t))
-                .SingleOrDefaultAsync(t => t.Id == request.TrackId, cancellationToken);
+                .SingleOrDefaultAsync(cancellationToken);
 
-            return track ?? Result<TrackApplicationResponse>.NotFound();
+            return track is null
+                ? Result<TrackApplicationResponse>.NotFound()
+                : Result.Success(track);
         }
     }
 }

Application/Users/Handlers/GetUserByIdQueryHandler.cs

@@ -14,10 +14,13 @@ namespace Musify.Application.Users.Handlers
         {
             var user = await database.Users
                 .AsNoTracking()
+                .Where(u => u.Id == request.Id)
                 .Select(u => UserApplicationResponse.FromEntity(u))
-                .SingleOrDefaultAsync(u => u.Id == request.Id, cancellationToken);
+                .SingleOrDefaultAsync(cancellationToken);
 
-            return user ?? Result<UserApplicationResponse>.NotFound();
+            return user is null
+                ? Result<UserApplicationResponse>.NotFound()
+                : Result.Success(user);
         }
     }
 }