Automated Tests: Detecting Invalid Use Cases

Hey guys! Let's dive deep into how we can make our automated tests even smarter, specifically when it comes to catching invalid use cases in our applications. We're talking about scenarios where things aren't quite set up right, like an OutputPort that's supposed to handle validation failures but doesn't have a validator backing it up. That's a recipe for trouble, and we want our tests to flag it ASAP.

The Challenge: Detecting Misconfigurations

In the realm of Robertscorp's Clean Architecture and Mediator patterns, ensuring everything is wired up correctly is crucial. Think of it like a complex machine – all the gears need to mesh perfectly. Our goal is to build automated tests that can act as quality control, verifying that all the components—InputPorts, OutputPorts, validators, and pipes—are playing their roles as expected. Specifically, we are looking at how to ensure that if an OutputPort implements InputPortValidationFailureOutputPort, there must be a corresponding validator in place. This is where things get interesting.

Understanding the Problem

Imagine an OutputPort designed to handle validation failures. If this port is wired up without a corresponding validator, it’s essentially a dead end. Errors could slip through the cracks, leading to unexpected behavior and potentially nasty bugs. Our tests need to be able to detect these kinds of misconfigurations automatically.

The Goal

We aim to create a testing mechanism that can identify these invalid use cases without adding unnecessary overhead to our production code. We want our tests to be smart enough to understand the relationships between components and flag any discrepancies.

Approach 1: Leveraging Service Registration Information

One idea we've been kicking around involves using the service registration information. If we register services as either "required" or "optional," our automated test validation functionality could use this information to understand the dependencies of our pipes.

How It Works

The basic idea here is that if a pipe needs a particular service, the test framework would know about it. We can use generic constraints on the pipe itself. So, if an InputPort and an OutputPort meet the constraints defined by the pipe, our system should expect a corresponding service implementation for that pipe and those specific ports. Think of it as a contract: if these interfaces are in place, a service must exist to handle the interaction.

The Catch

The tricky part is figuring out which generic parameters of the service implementation match the generic parameters of the pipe. It's not always obvious, and if the parameters don't align correctly, we're back to square one. Imagine trying to fit a square peg in a round hole – that's the kind of headache we're trying to avoid.

Example

Let’s say we have a pipe that handles validation. It might have generic constraints like InputPort<T> and OutputPort<T>. The service implementation would also have its own generic parameters, but mapping them to the pipe's parameters might not always be straightforward.

Approach 2: The GetRequiredServices Interface

As an alternative, we could introduce an interface specifically for pipes. This interface would provide a way to determine the required services for each matching InputPort and OutputPort.

The Interface

We’re thinking of something like this:

Type[] GetRequiredServices(Type inputPort, Type outputPort);

This method would take the InputPort and OutputPort types as input and return an array of Type objects representing the services that are required for those ports to function correctly with the pipe.

Example Implementation

Let's take the InputPortValidationPipe as an example. Here’s how the GetRequiredServices method might be implemented for this pipe:

GetRequiredServices(Type inputPortType, Type outputPortType) =>
    [typeof(InputPortValidator<,>).MakeGenericType(inputPortType, typeof(TValidationFailure))];

In this case, the method would return the type of the InputPortValidator that is required for the given InputPort and the TValidationFailure type. This gives our test framework a clear indication of what services need to be present.

Benefits

This approach offers a clean and explicit way to define service dependencies. It makes it easy for the test framework to inspect a pipe and determine exactly what services are needed for it to function correctly.

Why Not Put This in Registration Code?

You might be wondering, “Why not just put this GetRequiredServices functionality directly into the pipe registration code?” That's a valid question!

The Problem with Production Overhead

Our main concern is adding unnecessary overhead to the production environment. This GetRequiredServices functionality is primarily for automated tests. Including it in the registration code would mean that every time a pipe is registered, this method would be executed, even though its only practical purpose is to assist with testing. That's extra work that our production application doesn't need to do.

Keeping Things Lean

We want to keep our production code as lean and efficient as possible. Adding test-specific logic to the registration process would violate this principle. It’s like carrying around a spare tire in your car all the time – it’s useful in emergencies, but most of the time, it’s just extra weight.

The Trade-off

There’s definitely a trade-off here. Putting the functionality in the registration code might make the tests slightly simpler to write, but it comes at the cost of increased complexity and overhead in the production environment. We believe that keeping the testing logic separate is the better approach in the long run.

Current Preference

At the moment, I'm leaning towards the GetRequiredServices interface approach. It provides a clear, explicit way to define the service dependencies of our pipes, and it keeps the testing logic separate from our production code. This aligns with our goal of creating robust automated tests without adding unnecessary overhead to the application.

Next Steps

We'll be experimenting with this approach in more detail, implementing the GetRequiredServices interface for various pipes and building tests that leverage it. We'll also continue to evaluate the service registration information approach to see if there are ways to make it more practical and less prone to ambiguity.

Let's Discuss!

What do you guys think? Are there other approaches we should consider? Any potential pitfalls we haven't thought of? Let's discuss this further and figure out the best way to make our automated tests as effective as possible!