public void Return_PostReply_Correctly_By_PostReplyId() { //Arrange var options = new DbContextOptionsBuilder <ApplicationDbContext>() .UseInMemoryDatabase(databaseName: "Get_Post_By_Id").Options; using (var ctx = new ApplicationDbContext(options)) { ctx.PostReplies.Add(new PostReply { Id = 221, Content = "Test Reply" }); ctx.PostReplies.Add(new PostReply { Id = 111, Content = "Second Reply" }); ctx.SaveChanges(); } //Act using (var ctx = new ApplicationDbContext(options)) { var replyService = new ReplyService(ctx); var reply = replyService.GetById(221); //Assert Assert.AreEqual(reply.Content, "Test Reply"); } }