Why Your Script Include Cannot Scale Without Dependency Injection in ServiceNow

[BillMartin]

A Message for ServiceNow Developers and Architects Building for Growth

As your ServiceNow implementation grows, so does the complexity of your code. You're adding more modules, more integrations, more logic — and before you know it, your script includes start to look like a tangled web of dependencies.

If you're finding it hard to maintain or extend your custom classes, the problem might not be your process or your team — it might be the lack of Dependency Injection (DI) in your Script Includes.

What Is Dependency Injection, and Why Does It Matter in ServiceNow?

Dependency Injection is a design pattern where components receive their dependencies from the outside, instead of creating them directly.

In ServiceNow Script Includes, this means passing in the services, repositories, or utility classes your logic depends on — rather than hardcoding them inside the class.

It's a simple but powerful shift that gives your code flexibility, testability, and long-term maintainability.

Why Your Script Include Can’t Scale Without It

Hardcoded dependencies lead to tight coupling. If your Script Include creates all the objects it needs inside itself, any change to one class could break multiple others. DI keeps your components decoupled, making changes safer.

It becomes difficult to test or mock. Without DI, you can’t easily isolate or replace parts of your logic during testing. With DI, you can inject test versions of services or repositories and validate your logic independently.

Code reuse becomes limited. Each Script Include that creates its own internal dependencies is duplicating logic. With DI, you inject shared logic — meaning more reuse and less maintenance overhead.

You lose flexibility to evolve. If you ever need to replace one part of your logic — a logging utility, a data source, or a configuration loader — hardcoded dependencies lock you in. DI lets you swap components without rewriting everything.

Your code will eventually break under complexity. The more logic you pile into a Script Include without DI, the harder it becomes to manage. As business needs evolve, you’ll spend more time fixing old code than delivering new value.

ServiceNow Doesn’t Enforce DI, But You Can Adopt It

ServiceNow doesn’t have a built-in dependency injection framework, but you don’t need one to apply the pattern.

You just need to stop instantiating dependencies inside your classes, and start passing them in.

This lets you inject different versions of a dependency (a real one, a mock one, or a cached one) depending on the context.

Benefits You'll See in Real Projects

Easier to unit test your logic
Safer to make changes without breaking everything
More reusable classes across different parts of the platform
Better long-term scalability as your application grows
Less time debugging hardcoded dependencies

Final Thought

If you’re building scalable, reusable, and testable logic in ServiceNow, your Script Includes need to support dependency injection.

It’s a simple shift in mindset — but one that will help you write cleaner code, manage complexity, and build solutions that actually grow with your business.

Watch my live demo to see Dependency Injection in Action

Have you started using dependency injection in your ServiceNow apps? Share your thoughts or tips — others in the community will benefit from your experience.