Why Arrange Act Assert Works So Well For AI Software Testing

AI testing shouldn't be some super complex thing that needs hours' of configuration to work effectively. Simplicity is the name of the game.

You build a test using natural language. You press a button. You get a result. Ultimately, AI will transform software testing into a 'black box' process, in which engineers won't need to know what's going on under the hood - and that's a good thing.

This is why Arrange Act Assert (AAA) is such a strong unit testing pattern for AI-automated tests. It's quick, it's simple, and it ramps up your find and fix rate because it makes it so easy to locate the cause of failed tests.

It also maps onto how AI testing tools work nicely.

If you're looking for a way to increase your test coverage, speed up your feedback loops, and get you close to that black box efficiency right now, AAA is the way forward. Here's why.

What is Arrange Act Assert?

'Arrange Act Assert' is an approach to structuring test cases when performing unit tests. Here's how the pattern works:

• Arrange the preconditions needed for the test case to ensure you're testing your code under the right circumstances. If, for example, your test needs any special settings, to prep a database, or to log into a web app, these operations should be handled during the 'Arrange' phase.
• Act on the target behavior. The functions covered in your 'Act' step should be the main point of the test - for example, submitting a form input on a webpage, navigating a user interface, or a user logging into your app, having signed up already.
• Assert which outcomes result in the test passing or failing. This can range from basic, functional scenarios (for example, a welcome email being sent successfully post sign-up) to more complex assertions that check multiple parts of the system you're testing.

In even simpler terms, you arrange the conditions necessary for the test to take place, you program the code to act on the behavior you're testing, then you assert which outcomes mean the test passes or fails.

Does This Sound Familiar?

If you're experienced with Behavior-Driven Development, and/or use Gherkin to automate some of your tests, you'll probably have heard of the 'Given When Then' (GWT) approach to creating tests.

This is very similar to AAA, but with a minor difference in focus. GWT encourages engineers to think in terms of behavior rather than the internal mechanics of the test. Neither is wrong - it's all about what works best for your team and how you structure your testing processes.

6 Reasons Arrange Act Assert Simplifies Your Testing Processes

1. Sticking to an AAA Testing Pattern Results In Clean, Easy-to-Follow Tests

If you've ever had to deal with poorly-structured tests that you didn't write, you'll understand how much of a difference a standardized test structure makes - particularly when you're under pressure from demanding deadlines.

By opting for a standardized structure across all your unit tests, you improve readability and improve team efficiency - both for the engineers that wrote the tests and other team members who may have to use, understand, or modify them further down the line.

2. AAA Leads to Faster Feedback Loops

When you use AAA, you're channeled into testing individual functionalities in isolation. This is a useful piece of testing best practice that allows you to immediately isolate a potential bug or issue.

And, if a test fails, the AAA testing pattern allows you to pinpoint the exact section of the test that didn't work - was the setup incorrect, did the app behave unexpectedly, or were the assertions too vague?

3. AAA Is Great at Testing Exceptions

Need a fast, efficient way of testing expected exceptions? Arrange Act Assert is your best friend.

With AAA, you can test both the standard operation of a feature after an action is taken, and its failure conditions. If you're expecting custom domain exceptions or use of guard clauses to meet input expectations, this is particularly useful.

4. AAA Encourages Independent Tests

To run reliably, tests should be independent of each other - you should be able to run all your tests in any order, without any of them affecting the outcome of another. An AAA structure for your unit test encourages this.

Test structure best practices to follow here include:

• Avoiding sharing states between tests
• Minimizing dependencies and unnecessary interactions with external resources
• Avoiding sharing states between tests and resetting modified states

5. AAA Offers Flexibility For Testing AI Features

If you're not testing AI features already,, it's likely you will be in the near future. Arrange Act Assert helps you navigate some of the unpredictability Gen-AI features introduce to your testing processes.

AAA encourages deterministic test scaffolding by setting everything up in the 'Arrange' step, which helps make tests more repeatable - even with the randomness gen AI brings. Engineers can also use fuzzy matching in the 'Assert' step to test complex LLMs or gen AI tools - there's no need to stick to rigid exact assertions.

6. AAA Tests Are Easy to Maintain

Your codebase will evolve over time, so your test suite should be able to evolve with it.

AAA tests' clear separation of concerns and predictable structure make them easy for your engineers to update. Your team spends less time maintaining and updating tests, and does so with fewer errors - and has more time to invest elsewhere as a result.

Arrange Act Assert tests also tend to keep setup and assertions decoupled from the implementation details, making them resilient to refactors in the code being tested.

AAA and AI Testing: A Match Made in Heaven

Following the AAA pattern doesn't just align your team with current testing best practices - it also makes it easier to use AI testing tools to increase coverage, speed up tests, and create easy-to-maintain code.

If you've invested in an AI testing tool, you want to get the most out of it. There's no point investing, implementing, then only realizing 50-60% of the efficiency gains you could enjoy.

On a basic level, having the same structure for every AI unit test brings:

• Repeatability
• Reliability
• Scalability

This means you can ramp up your test coverage practically overnight, especially when using natural language processing to build new tests. You have the structure - all you need to do is type in what you want the test to do.

Here's a quick example of what this might look like in practice, if you were testing a basic login process for a web app:

// Arrange
NAVIGATE to "https://example.com"

// Act
TYPE "username" into "username input"
TYPE "password" into "password input"
CLICK "login button"

// Assert
AI_ASSERTION "login success message"

Many AI testing frameworks are built around Arrange Act Assert or Given When Then structures already. This means it's very easy to automate AAA tests with AI

• and, the more you test, the easier it is for AI agents to automatically generate tests based on the expected behavior of your app.

AAA Is an Ideal Companion For Natural Language Models

One of the most useful features of modern AI testing tools is that you can build tests in natural language - just tell the tool what you want using plain English, and the AI will build the test for you.

We naturally tend to be less direct and more conversational when using human language over code, and there's a risk that this lack of direct instruction can translate into poorly-constructed tests. By using AAA as a framework to structure your tests, you ensure that they are stable and produce reliable results (even when your coding brain is switched off).

Momentic + Arrange Act Assert: Your Testing Efficiency Cheat Code?

"Momentic makes it 3x faster for our team to write and maintain end to end tests."
Alex Cui, CTO, GPTZero

We'd love to see if Momentic's AI testing tools could help you optimize your software testing life cycle.

If, like Alex and his team, you're keen to save over two thirds of the time you spend on key testing processes, why not schedule a conversation with our founder?