Why We Write Unit Tests for NetSuite Code (Even When It Feels Optional)

Unit testing in the NetSuite ecosystem isn't common practice—and we get why.

SuiteScript isn't exactly test-friendly out of the box. You're dealing with system modules, record APIs, governance quirks, and often very business-specific logic. But skipping tests doesn't make those challenges go away. It just pushes the cost downstream—into QA, production fixes, and repeated bugs.

We've learned that unit testing is one of the fastest ways to save time long-term—and it doesn't have to be painful.

The Reality Check: Why Most Teams Skip Unit Testing

Before diving into solutions, let's acknowledge the elephant in the room. Most NetSuite development teams don't write unit tests, and there are legitimate reasons why:

• Time Pressure: Project deadlines feel more urgent than writing tests that "don't deliver features."
• Complex Environment: NetSuite's architecture makes traditional testing approaches feel cumbersome.
• Knowledge Gap: Many developers haven't experienced the long-term benefits of a well-tested codebase.
• "It Works" Mentality: If the script runs without errors, it must be fine, right?

Here's the problem: what feels like saved time upfront becomes technical debt that compounds over every project phase.

Why We Unit Test (Especially in ERP Projects)

In our experience working with NetSuite implementations across industries, unit testing delivers measurable value:

• Catch Logic Errors Early: Before they waste time in QA or UAT. Finding a calculation error in your test suite takes minutes. Finding it during user acceptance testing can derail a go-live timeline.
• Protect Critical Code from Future Changes: Refactor safely without fear. When business requirements evolve (and they always do), tests give you confidence that changes won't break existing functionality.
• Make Code Easier to Understand and Maintain: Tests clarify intent. New team members can read your tests to understand what the code should actually do, not just what it appears to do.
• Encourage Better Structure: Testable code is usually cleaner code. Writing tests naturally pushes you toward modular, focused functions that do one thing well.
• Onboard New Developers Faster: Tests act as living documentation. Instead of spending weeks understanding legacy code, new team members can read tests to grasp business logic quickly.

How We Write Unit Tests for SuiteScript

The key insight: isolate the logic from the platform.

Instead of testing scripts directly inside NetSuite, we break logic into plain JavaScript or TypeScript modules—then test them outside NetSuite using tools like Jest.

A Practical Example

Here's how we structure testable NetSuite code:

_{// batchHelper.ts}

_{export function assignBatchKey(payment: Payment): string {}

  // some logic here

_}

_{// batchHelper.test.ts}

_{import { assignBatchKey } from “./batchHelper”;}

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_{describe(“assignBatchKey()”, () => {}

  it(“assigns correct batch key for given payment”, () => {

    const payment = { id: 123, type: “vendorpayment”, date: “2025-08-02”};

    const key = assignBatchKey(payment);

    expect(key).toBe(“VENDORPAYMENT_20250802”);

  });

_});

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This approach allows us to test logic thoroughly without SuiteScript dependencies slowing us down. We can run hundreds of test cases in seconds, catching edge cases before they reach production.

What We Test (and What We Don't)

We Test:

• Business Logic: Tax calculations, batch key assignments, approval workflows
• Data Transformations: Cleaning or mapping records before submission
• Reusable Helpers: Utilities, validators, and logic extractors

We Don't Test:

• NetSuite's Native APIs (we mock them instead)
• UI Scripts or Inline Suitelets (we test those through behavior, not units)

Real-World Impact: A Case Study

In one client's codebase, we had a calculateWithholdingTax() function that behaved differently depending on vendor classification and transaction type. It worked fine in initial testing—until one edge case caused it to silently undercompute tax by thousands of dollars.

After extracting it into a helper module and writing comprehensive unit tests, we discovered 3 more cases we hadn't accounted for. We fixed all of them in 30 minutes—and kept the tests in place to prevent regressions.

‍Build Confidence in Your NetSuite Development

Unit tests may feel like overhead at first—but they're one of the few things that consistently reduce bugs, speed up onboarding, and make you fearless during refactors.

In NetSuite projects where every error burns governance and QA cycles, testable code is durable code.

At ATSOURCE, we’ve learned over more than a decade that sustainable NetSuite development takes more than just making scripts work—it requires making them work reliably, maintainably, and confidently over time.

Ready to build more robust NetSuite solutions? Let's discuss how ATSOURCE can help you implement testing practices and development workflows that scale with your business growth.

Meet the Author

Jona has over a decade of experience in SuiteCloud Development on the NetSuite platform. She specializes in implementing advanced solutions and has led teams in creating high-quality software. Jona holds multiple certifications and has been recognized with awards like the Summit Award and Quality Champion Award.

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