Adding unit tests

Services/BlacklistService.cs

@@ -17,13 +17,13 @@ public class BlacklistService
         _blacklist = db.GetCollection<BlacklistedToken>("BlacklistedTokens");
     }
 
-    public async Task AddToBlacklistAsync(string token, DateTime expiry)
+    public virtual async Task AddToBlacklistAsync(string token, DateTime expiry)
     {
         var entry = new BlacklistedToken { Token = token, Expiry = expiry };
         await _blacklist.InsertOneAsync(entry);
     }
 
-    public async Task<bool> IsTokenBlacklistedAsync(string token)
+    public virtual async Task<bool> IsTokenBlacklistedAsync(string token)
     {
         var exists = await _blacklist.Find(x => x.Token == token && x.Expiry > DateTime.UtcNow).FirstOrDefaultAsync();
         return exists != null;