SAP S/4HANA Migration: Why Testing is Essential for a Successful Migration

Since support for SAP ECC and SAP R/3 will end in 2027, many companies are under increasing pressure to modernize their ERP landscape. For most, there is hardly any way around SAP S/4HANA.

The migration to S/4HANA, however, is anything but straightforward. Many projects go over budget, miss deadlines, or fail to deliver the expected business value—even though the ERP system is business-critical for nearly all companies. Why is that? Migration is not just a technical upgrade but a profound business and organizational transformation. For example, many companies fail to critically assess or redesign their existing business processes. Instead, they carry over old inefficiencies into the new system landscape. Without a solid QA strategy and the use of automation, not only do technical risks loom, but also costly disruptions to ongoing operations.

In this article, we highlight the most common testing gaps that lead to delays and additional costs, and show you how to develop a QA strategy that secures your project and protects your business.

The Hidden Risk: Underestimating Testing

A central reason for difficulties in S/4HANA migrations is often insufficient or delayed testing.

Too often, companies focus primarily on transferring existing business processes from the old to the new version as well as migrating legacy data. In doing so, they not only miss opportunities for process optimization but also frequently neglect structured quality assurance: documentation remains incomplete, testing is mostly manual, and clear quality criteria are often lacking.

The consequences can be severe:

• Business operations are unexpectedly disrupted.
• Customer service comes to a halt.
• The accuracy of financial reporting suffers.

These are not just IT issues—they are critical business risks. Given the urgency of the ECC support deadline, companies cannot afford to treat testing as an afterthought.

Understanding the Challenge

SAP landscapes are rarely simple. Over the years, layers of custom code, third-party integrations, and team-specific workarounds accumulate within the systems. In most companies, SAP touches nearly every business function—from finance and logistics to HR, sales, and production. Migrating this ecosystem to S/4HANA is not a simple copy-paste exercise. The new system brings architectural simplifications, functional redesigns, and updated best practices. This requires a careful rethinking of how business logic is executed—and how it should be tested.

Where Things Start to Go Wrong: No Test Strategy at Kick-off

Many S/4HANA projects begin with a strong focus on infrastructure, system sizing, and data migration. Kick-off meetings revolve around timelines, go-live goals, and resource allocation. Testing, however, is often overlooked—or treated as something that can be dealt with “later.”

This frequently leads to several pitfalls:

• Test teams are brought in too late and without sufficient understanding of business processes.
• Quality gates are not clearly defined, making it difficult to measure system readiness.

Instead of structured test plans, teams rely on unplanned, ad hoc tests that are neither documented nor repeatable—resulting in inconsistencies and avoidable risks.

Common Assumptions – Often Too Short-Sighted

• “We’ll just carry over what the old system did.”

This often results in outdated processes being migrated, while potential quick wins are left untapped.

• “The users know the processes.”

Without thorough analysis, gaps and contradictions remain. Users typically only know their own functional area and lack visibility of the bigger picture.

These simplified assumptions overlook an important fact: migrations require a verified understanding of both the as-is and the to-be state. Without this understanding, it is impossible to plan effective tests—and success remains uncertain.

Documentation Is Not Optional – It’s Foundational

Proper documentation is often dismissed as extra effort—but in SAP transformation projects, it is non-negotiable. You can’t test what you can’t describe. Documentation is the blueprint for every test you conduct, and here’s what good QA documentation should include:

1. Core Test Assets

• Test plans that define scope, responsibilities, and entry/exit criteria
• Test cases based on real usage scenarios (not just positive paths)
• Traceability matrices linking business requirements to tests

2. Process and System Knowledge

• As-is and to-be process flows
• Interface diagrams showing system interactions
• Data flow documentation and transformation logic

3. How to Build This Efficiently

• Run documentation workshops with business stakeholders
• Extract click paths directly from existing SAP environments
• Use reverse-engineering tools such as Solution Manager or Signavio

Without this foundation, QA teams are left guessing what and how to test. This leads to incomplete validation, last-minute scrambling, and errors that only surface in production. The result? Delays, costly rework, and disruption to business operations.

The Reality of Custom Code and New Processes

Most mature SAP systems are full of custom developments. These elements rarely survive migration unchanged. In S/4HANA, many need to be rewritten or adapted due to architectural changes. However, custom code is often migrated without proper unit testing. This leads to hard-to-detect errors that surface late and can bring critical processes—such as invoicing, payroll, or supply chain execution—to a standstill.

At the same time, S/4HANA introduces new standardized processes based on best practices. Yet these are often validated only in isolation—using test data rather than real migrated historical data. The result is that workflows fail in production because key data fields are missing or behave differently than expected.

Data and Integration Risks Are Often Invisible

Even if code migration is done correctly, data and interface testing remain dangerous weak spots.

- Hidden data-mapping errors

Data transformation during migration is not always one-to-one. If mapping rules are not fully validated, critical fields may be skipped or filled incorrectly. These errors often go unnoticed—until they cause bigger issues in downstream processes.

- Fragile interfaces

S/4HANA rarely operates standalone. It connects with third-party tools such as WMS systems, payment gateways, logistics providers, and HR platforms. Testing these interfaces, however, requires coordination, test environments, and planning. Many teams skip this step, assuming things will “just work” as before.

- Siloed testing = broken end-to-end flows

Testing often happens module by module. But business processes such as order-to-cash or procure-to-pay span multiple areas. Without cross-functional collaboration, these flows are rarely tested end-to-end—leading to operational disruptions after migration.

Why Manual Testing Isn’t Enough

Manual testing has its place—but S/4HANA migrations require more. End-to-end workflows in SAP often span multiple modules, teams, and external systems. Simulating these flows manually is:

• time-consuming
• error-prone
• impossible to repeat consistently

Where Test Automation Delivers the Greatest Business Value

Regression testing

Automated validation of custom code and standard functions after every update. This frees testers to focus on new features while increasing test coverage.

Data reconciliation

Automated comparison of legacy and S/4HANA data across thousands of records. This helps identify inconsistencies early and minimizes go-live risks.

End-to-end flows

Simulation of realistic, cross-module processes such as order-to-cash or procure-to-pay. This improves process reliability and uncovers integration issues before go-live.

UI automation

Automated interaction with SAP GUI or Fiori apps using tools like CBTA, Tricentis Tosca, or Selenium. This speeds up testing and ensures consistency across interfaces.

Performance scripts

Synthetic load testing of critical batch processes like payroll or month-end closing. This exposes performance bottlenecks before they disrupt operations.

By automating these processes, companies can reduce test cycles from weeks to days without sacrificing coverage. Organizations that fail to invest in test automation often discover critical errors only at cutover—or worse, after customers and business users are already affected.

The Missing Ingredient: Test Automation

A compelling example comes from our proof of concept with ALDI SÜD, one of the world’s largest grocery retailers. There, we demonstrated that end-to-end test scenarios can be automated even in highly complex, international SAP environments. The PoC proves that test automation is both feasible and effective.

This example can serve as a guide for other SAP customers, as most face similar challenges:

- No regression suite Most teams rely on manual regression tests that cannot scale. Without automated testing, updates become increasingly risky, and even small changes require full manual retesting.

- Underused SAP test tools SAP provides tools such as CBTA and Tricentis designed for business process testing. But due to time pressure, lack of expertise, or limited awareness, they’re often ignored—a missed opportunity to quickly compare old and new system behavior and detect discrepancies before they become issues.

- Skipping performance tests Few projects simulate peak loads—such as month-end closing, Black Friday, or quarter-end. Without advance performance testing, unexpected slowdowns or outages can occur at exactly the moments when reliability matters most.

Conclusion: Testing Is the Decisive Factor

A successful S/4HANA migration requires meeting a wide range of demands—from IT infrastructure and performance, to processes and data models, to role models, interfaces, and more. At the same time, it also requires an accompanying QA strategy focused on:

1. A scalable testing concept from day one
2. Structured, documented validation of customizing and standard processes
3. Automation to perform regression and performance testing
4. Real-world testing with live data and complete workflows

Neglecting testing may save time in the early phases—but it is the main reason why SAP migrations go off track.

At andagon, we help SAP customers avoid costly testing pitfalls by providing:

• Design of a test strategy tailored to the S/4HANA architecture
• Test automation with CBTA, Tricentis, and beyond
• Integration validation in complex environments
• Performance simulations before peak times occur

Get in touch with us for an SAP QA assessment—and let’s reduce your migration risk before it’s too late.