By William Perez, SAP Principal Engineer at Foulk Consulting
As the deadline for SAP S/4HANA migration draws closer, the debate in boardrooms usually centers on one question: Greenfield or Brownfield?
For those seeking a “fresh start,” Greenfield is the siren song—a chance to abandon decades of clunky customizations and return to standard processes. But for the vast majority of enterprise organizations, the reality is Brownfield. Whether it’s due to the sheer volume of historical data, the complexity of existing business logic, or the need to minimize operational disruption, converting an existing ECC system into S/4HANA is the path most traveled.
However, there is a dangerous misconception that because a Brownfield migration “keeps what you have,” the testing effort is simpler.
In reality, it’s the opposite. If you are choosing Brownfield, your testing strategy must undergo a fundamental shift—or you risk being buried by the technical debt you’ve chosen to inherit.
The “Clean Slate” vs. The “Inherited Reality”
In a Greenfield implementation, testing is largely about validation. You are building new processes and ensuring they meet business requirements. You are starting with a clean slate, meaning your test surface area is defined by the new scope you create.
In a Brownfield conversion, you aren’t just moving data; you are moving an ecosystem. You are inheriting:
- Years (often decades) of custom Z-programs.
- Intertwined third-party integrations.
- Manual workarounds that have become “mission-critical.”
- Technical debt that has been hidden in the corners of your ECC environment.
When you move this “inherited reality” to S/4HANA, the HANA database and the new simplified data model change the rules of the game. Code that worked yesterday may fail today—not because the logic is wrong, but because the underlying architecture has shifted.
Why Traditional Testing Fails in Brownfield
The old way of testing—the “test everything” or “regression test the most important 50 scripts” approach—is a recipe for failure in a Brownfield migration.
If you try to test everything, you will never go live. The timeline and cost will spiral out of control. If you only test the “most important” things based on gut feeling, you will inevitably miss a critical custom object that fails in production, leading to a “Hypercare” period that feels more like a disaster recovery operation.
In Brownfield, you don’t need more testing. You need Risk-Based Testing.
Enter LiveCompare: The Precision Advantage
At Foulk Consulting, we advocate for a shift toward AI-driven impact analysis. Specifically, we leverage Tricentis LiveCompare to bridge the gap between “we think this is safe” and “we know this is safe.”
LiveCompare acts like an MRI for your SAP landscape. Instead of guessing which parts of your system will be affected by the S/4HANA conversion, it analyzes your specific custom code and usage patterns. It identifies exactly which objects are impacted and, more importantly, which ones are actually used by your business.
Why this is a game-changer for Brownfield migrations:
- Eliminating the Noise: Why waste time testing a custom report that hasn’t been run since 2014? LiveCompare identifies used vs. unused code, allowing you to decommission the “junk” and focus your testing energy where it matters.
- Pinpointing the “Hot Spots”: It shows you exactly which standard and custom transactions will be impacted by the move to S/4HANA. This allows us to create a “Smart Test Gap” report—showing you what needs to be tested and where your current test library is lacking.
- Reducing Effort by 85%: By shifting from a “test everything” mindset to a “test what changed” mindset, we typically see a massive reduction in the manual testing effort. This isn’t just about saving time; it’s about increasing the quality of the migration.
The Bottom Line
Choosing a Brownfield path is a strategic decision to preserve your unique business DNA. But that DNA comes with mutations—technical debt that can jeopardize your S/4HANA journey if handled poorly.
If you are migrating your legacy system, you cannot rely on legacy testing methods. You need a strategy that is as sophisticated as the system you are building. By embracing risk-based testing and tools like LiveCompare, you can turn the “risk” of Brownfield into a controlled, predictable, and successful transformation.
Is your testing strategy ready for the move to S/4HANA? At Foulk Consulting, we specialize in helping organizations navigate the complexities of SAP migrations with precision and confidence. Let’s discuss how we can optimize your testing roadmap.
