Handling Session Deletion Exceptions: A Comprehensive Guide

by Lucas 60 views

Hey guys! Let's dive into a crucial aspect of software development: handling exceptions during session deletion. Specifically, we'll explore the CTU051 scenario, where we aim to ensure our system gracefully manages failures when deleting a session. This is super important because it helps us build robust and reliable applications. When things go wrong, we want our systems to handle it elegantly, providing informative error messages and preventing data corruption. So, grab a coffee, and let's get started!

Understanding the Objective: Returning Failure on Deletion Exceptions

Our primary objective is to design the system to return a failure when an exception occurs during the session deletion process. This means that if something goes wrong while attempting to delete a session, we want the system to recognize the error, report it appropriately, and take the necessary steps to prevent further issues. Think of it like a safety net – it's there to catch any problems and protect the integrity of our application. This is what we call exception handling, which is a cornerstone of good software design. Without proper exception handling, our application could crash, lose data, or behave unpredictably. In this specific CTU051 case, we are aiming at ensuring the system behaves as expected when an exception is thrown while we are trying to delete a session. This is key to maintaining data integrity and providing a smooth user experience.

Why is this important?

Imagine you're trying to delete a session, but there's a hiccup in the database connection or some other technical glitch. Without proper exception handling, the whole deletion process could fail silently, leaving the user confused or worse, leading to inconsistent data. By proactively handling exceptions, we can provide clear feedback to the user, allowing them to understand what went wrong and potentially try again or contact support. Moreover, proper exception handling can also prevent the application from crashing, making it more stable and reliable. This is especially critical in enterprise-level applications or systems where data integrity and availability are of the highest importance. This is about building resilient applications. When exceptions are handled correctly, you can provide a better user experience and ensure the system functions as expected, even when encountering unexpected circumstances.

Prerequisites: Setting the Stage for Failure

Before we get into the nitty-gritty, let's clarify the prerequisites. We need to set the right conditions to simulate the failure scenario. These prerequisites define the starting point and the environment in which the deletion process takes place.

Precondition Breakdown:

  1. SelecionarRegistros() contains the session: This means that the session we intend to delete actually exists in the system. We need to ensure that our deletion process is trying to delete a session that is actually present. This is our starting point, the session exists and can be selected. This step is fundamental to allow the deletion process to work; if the session is not found, it cannot be deleted.
  2. Excluir(id) throws an exception: This is where we introduce the failure. The Excluir(id) method, which is responsible for deleting the session, will be programmed to throw an exception. It might be due to a database error, a permission issue, or any other reason that prevents the deletion from succeeding. This simulates the failure scenario we are testing.
  3. Act uses a non-existent Id (without Commit()): The Act step will use an ID that does not exist. Also, the system is not allowed to Commit() the changes. This is also crucial because it lets us test the application's ability to handle an incorrect ID when attempting to delete a session. It helps to make sure that our system can distinguish between various types of errors.

These prerequisites are key to ensure we can properly test the handling of exceptions during session deletion. They will set the scene for us to reproduce and validate the exception handling mechanisms we want to implement. This way, we can simulate a real-world failure scenario and see how our application behaves under stress.

Step-by-Step: Orchestrating the Failure

Alright, let's walk through the steps required to trigger and verify our exception handling mechanism. These steps outline the actions that should be performed, as well as the expected outcomes. It is like a recipe for testing exception handling.

The 'Arrange' Phase:

  1. Sessao novaSessao = new(inicioPadrao, 30, filmePadrao, salaPadrao): We'll start by creating a new session object with initial parameters. This sets up the context for our deletion operation. This is the creation of an instance of the session, setting up the foundation for our simulation.
  2. mockar SelecionarRegistros() -> [ novaSessao ]: We mock the SelecionarRegistros() method to return our newly created session. This simulates the existence of the session in the system. It makes sure that the deletion is trying to delete something that actually exists.
  3. repositorioSessaoMock.Excluir(novaSessao.Id) lança Exception: The mock for the Excluir() method in the session repository is set up to throw an exception. This is what simulates the failure we are trying to test. This is the critical step where the exception is triggered, mimicking a database error or another failure during the deletion process.
  4. unitOfWorkMock.Commit() lança Exception: The mock for Commit() will also throw an exception. This ensures that the changes are not saved into the database. This stage makes sure that changes are not committed. This safeguards the database from inconsistent states caused by the failure.

The 'Act' Phase:

  • Result resultadoExclusao = sessaoAppService.Excluir(Guid.NewGuid()): We call the Excluir() method on the session application service. We pass a new Guid, which does not exist. This is the core of the action we are testing – attempting to delete a session. This initiates the process, triggering all the underlying operations.

The 'Assert' Phase:

Now we reach the important part, the verification phase. It is like checking the final product to ensure it meets our expectations.

  1. unitOfWorkMock.Verify(Commit(), Times.Never): We verify that the Commit() method was never called on the mock unitOfWork. This verifies that the changes were not saved into the database, which means that the transaction was rolled back due to the error. This prevents any data corruption.
  2. IsNotNull > resultadoExclusao: Check if resultadoExclusao is not null. It assures that the system returns something and the operation does not silently fail.
  3. IsTrue > resultadoExclusao.IsFailed: We assert that the resultadoExclusao.IsFailed flag is set to true. This indicates that the session deletion operation failed as expected. It validates that our system is correctly recognizing the failure.
  4. `AreEqual >