Public sector system migrations: why QA can’t be an afterthought

Imagine a government department is preparing to migrate decades of citizen data from a legacy system. The system has served hundreds of thousands of people for years, but it’s slow, expensive to maintain, and vulnerable to security risks. The migration is intended to modernise services and improve efficiency - but one misaligned data field or overlooked transformation could mean incorrect benefits, delayed healthcare, or misallocated payments.

This isn’t a hypothetical risk. In a public-sector system migration, every record, every transaction, every workflow matters. And yet, too often, QA is left until the final stages of the project - treated as a checkpoint rather than a continuous safeguard.

Most data migrations don’t fail because of engineering

It’s a common misconception that migrations fail because of bad code. In reality, the problem usually comes down to QA. When testing is left until the end, reconciliation becomes reactive, and teams often don’t know what went wrong - or when. Uncontrolled QA debt accumulates until the final cutover, creating panic, cost overruns, and sometimes, service failures.

Embedded QA changes that story. Continuous migration testing catches small problems early, validates data as it moves, and gives teams confidence that the project is on track. When QA is part of the foundation rather than a final checkpoint, the whole migration becomes smoother and more predictable.

The hidden risks of legacy systems

Legacy systems often carry surprises. They can be poorly documented, tightly coupled, or riddled with edge cases that nobody fully understands. Migrating them without a clear QA strategy is risky.

QA mitigates these risks. By testing incrementally, validating transformations, and running integration checks, teams can make sure everything works together as intended. QA also provides audit trails, so regulators and stakeholders can see that critical services and data are protected.

Quality assurance is a strategic enabler

QA isn’t just about spotting bugs - it can shape the way the migration is planned and executed. A strong QA strategy starts with understanding the data, identifying key transformations, and agreeing on success criteria. Automated tests, synthetic datasets  , and continuous feedback loops reduce human error and accelerate confidence in results.

Non-functional testing - checking performance, security, and accessibility - ensures the system isn’t just correct, but also ready to handle real-world use. In short, QA turns a potentially stressful migration into a controlled, predictable process that benefits both the organisation and the people it serves.

Lessons from Southern Housing

Our work with Southern Housing demonstrates this principle in action. Since 2019, we’ve supported the housing association through multiple transformation programmes, including their merger with Optivo. These projects required careful migration of complex datasets while maintaining service continuity for residents.

Our team worked closely with Southern Housing’s implementation managers to design a QA strategy that integrated into every stage of the migration. We managed test delivery across multiple workstreams, executed end-to-end testing frameworks, and carried out rigorous integration testing during the merger to ensure that all systems and workflows interacted correctly after combining platforms. Continuous validation confirmed that the data and system functionality remained accurate and reliable.

The result? Southern Housing could modernise with confidence, knowing that critical resident data was secure, accurate, and fully reconciled. By embedding QA throughout the process, they avoided last-minute panic, reduced risk, and delivered a smoother, more reliable transition.

Building a culture of continuous QA

The most successful migrations aren’t just about processes - they’re about culture. Cross-functional collaboration, transparency in reporting, and the strategic use of automation ensure that quality is everyone’s responsibility. When QA is embedded as a continuous priority, it becomes a safety net that prevents errors from escalating and reduces operational risk.

System modernisation without compromise

Public-sector migrations are complex, high-stakes, and mission-critical. Done right, they enable secure, efficient, citizen-focused digital services. Done poorly, they jeopardise public trust, regulatory compliance, and budgets.

By treating QA as a foundation rather than an afterthought, agencies can protect data, minimise service disruption, ensure compliance, and reduce costs. Modernisation isn’t just about new technology - it’s about executing a reliable, trustworthy transition. Embedded QA is the key to making that happen.

Six key takeaways:

1. QA is foundational, not an afterthought - continuous testing and validation prevent last-minute panic and uncontrolled QA debt.
2. Legacy systems hide risks - poor documentation, tightly coupled modules, and edge cases make incremental, strategic QA essential.
3. QA is a strategic enabler - beyond catching bugs, QA improves performance, security, compliance, and the overall success of the migration.
4. Embedding QA reduces operational risk - integrating QA across all stages ensures data integrity, seamless service continuity, and stakeholder confidence.
5. Culture matters - cross-functional collaboration, transparency, and automation make QA a shared responsibility rather than a siloed task.
6. Modernisation succeeds with proactive QA - treating QA as continuous and embedded enables reliable, citizen-focused service delivery and protects public trust.

About Zoonou

Zoonou is a UK-based software testing company. We’re a B Corp and 100% employee owned. Combining technical delivery and advisory services, we collaborate with the private, public and third sectors to create better software, services and products.