Legacy software testing services
QA for systems that can't afford downtime
Maintain your solution and deploy fixes without fear. Migrate with proof, not hope. Partner with software testing experts that have hands-on experience and a proven track record.
Trusted by Fortune 500 companies across the globe since 2011.
What we help with
Maintain, improve, integrate, or migrate. We have your back.
Whatever stage your system is in, the testing approach fits the goal, not the other way around.
Software maintenance
Keep the current system stable and secure, with regression coverage on every change.
Feature expansion
Ship new features on the existing stack, verified against everything that already works.
Integration & interoperability
Connect legacy systems to modern tools and vendors without disrupting what already works.
Migration & modernization
Move to a modern tech stack with behavioral proof that nothing gets lost on the way.
Tell us your stack.
We've probably* worked with it.
COBOL, Delphi, VB6, .NET Framework, AS400, Oracle Forms. If it runs your business or you plan to migrate, we can help with the QA part.
*If we don't have the experience you need, Starbucks is on us.
Technical capabilities
How quality experiences get built on a legacy stack
The four goals above rest on six technical capabilities. This is the engineering layer: how coverage actually gets built on a stack that predates the tools everyone else uses.
Characterization & regression testing
The technical foundation of every legacy engagement: capturing current behavior as the specification. Golden master and snapshot techniques record real outputs (reports, files, database states, API responses) and flag any deviation on every run, wired into automated regression suites even where no CI pipeline exists yet.
- Golden master / approval testing against real production-shaped data
- Risk-based coverage mapping: highest-traffic and highest-revenue paths first
- Test execution integrated into legacy build systems (or built from scratch: Jenkins, scheduled runners, pre-release gates)
Migration & parity verification
The technical proof layer for replatforming: demonstrating, case by case, that the new system reproduces the old one's behavior. Covers tech stack migration, environment migration (on-premise to cloud, infrastructure and hosting moves), and combined scenarios.
- Behavioral parity suites: identical inputs run against old and new, outputs diffed automatically
- Data migration reconciliation: row counts, checksums, field-level comparisons across full datasets, not samples
- Parallel-run validation with automated divergence reporting; rollback readiness verified before each cutover gate
- Environment parity checks: configs, timezones, locales, OS dependencies, performance baselines on new infrastructure
Custom test harnesses for unsupported stacks
When Selenium, Playwright, and even AI-based tools fall behind, we simply have to build something custom - and that's what we have been doing since 2011.
- Terminal emulation for green-screen flows (AS400 / IBM i, 5250/3270 protocols)
- Desktop UI automation: WinForms, WPF, MFC, Delphi, VB6, Java Swing, PowerBuilder
- Protocol-level testing: SOAP, WCF bindings, MSMQ / legacy JMS queues, EDI, batch job orchestration
- Test data generation and masking for systems with production-only datasets
Executable documentation
The by-product that outlives the engagement. Every characterization test is a readable statement of what the system does. Business rules extracted from code and validated with your domain experts become specifications that stay accurate because they run daily.
- Behavior-level test descriptions readable by non-developers
- Business-rule extraction from stored procedures, batch logic, and code paths
- Traceability between rules, tests, and the modules that implement them
Integration & interface testing
The seams between old and new carry most of the incident risk: a modern API assuming the legacy core behaves one way, while it quietly behaves another. Contract-level testing pins down both sides.
- Contract testing between legacy cores and REST/GraphQL layers
- SOAP/WCF to modern service consistency checks, including fault and timeout behavior
- Batch-to-event-stream verification: ordering, duplicates, idempotency, reprocessing
- Third-party integration regression across system boundaries
Performance & load testing on legacy infrastructure
Capacity as a measured number, not a guess. Load testing tuned for closed, on-premise, and protocol-constrained environments where SaaS load tools can't reach.
- Load generation against legacy protocols and desktop/terminal sessions, not just HTTP
- Bottleneck isolation in aging databases, middleware, and batch windows
- Performance baselines captured pre-migration, compared post-migration
The process
Our engagement explained
Handing over a legacy system takes real trust. Here's precisely what happens at each stage, so nothing is a surprise.
- 1
Discovery
System, integrations, and risks mapped with your team. Broader starting point available via QA audit.
- 2
NDA & secure access
ISO 9001 / 27001 / 22301 certified processes. Your code is read by engineers under contract, never pasted into a public AI chatbot.
- 3
Behavioral baseline
What the system actually does today, documented. The reference point for every change and migration.
- 4
Coverage build-out
Highest-risk areas protected first. Value from the first sprint.
- 5
Safety net or migration support
Continuous regression protection, or full migration validation. Either way, covered.
- 6
Ongoing support
Scope flexes as your needs change, from steady-state maintenance to a future migration, without starting over.
Get yourself a partner that takes responsibility for QA activities
Our job is to help you ensure your system is running as it should, no matter what changes or improvement you plan.
Technologies
Legacy and aging technologies we know how to test
"Legacy" isn't just mainframes. It's also the .NET app from 2012 that processes every invoice, the VB6 tool nobody wants to touch, and the AS400 system running quietly in the background. If it's still doing real work, we know how to test it.
Microsoft stack
.NET Framework (WebForms, WinForms, WPF, MVC 3–5) · WCF & SOAP · VB6 & VB.NET · Classic ASP · Silverlight · SQL Server stored-procedure logic · COM/ActiveX
Languages & platforms
COBOL · Delphi · PowerBuilder · Legacy Java (6–8, EJB, Swing, Struts) · Perl · PHP 5.x · Python 2 · ColdFusion · FoxPro · Objective-C
Aging web frameworks
AngularJS · jQuery frontends · Backbone.js · Knockout.js · GWT · Flash/Flex · Rails 2–4
Systems & infrastructure
AS400 / IBM i · Mainframes · Oracle Forms · On-premise monoliths · MSMQ, old JMS
Interfaces
Green-screen terminals · Desktop clients (WinForms, MFC) · Batch pipelines · EDI
Your tech stack isn’t on the list? Let’s talk about it
Why clients choose us
Reasons companies trust us with legacy systems
Legacy software testing isn't just a side offering, it's specialized work with specialized proof. Here's what that actually looks like in practice.
500+ ISTQB certified engineers
Every engineer working on your system has met an internationally recognized testing standard, not just internal training, many with specific experience on older stacks most new hires have never touched.
14+ years in business
Long enough to have tested systems through multiple platform shifts and regulatory changes, and to have built the custom tooling that fills the gap when Selenium, Playwright, or AI-based generators can't reach a technology
5,000+ real devices and configurations
For legacy desktop clients still running on a mix of OS versions and hardware in the field, testing happens on real machines, not a single clean environment.
Human judgment where AI falls short
AI-generated tests drift into fiction on undocumented systems with no clean spec to train against. Our engineers read the code and verify the behavior directly.
Knowledge that compounds
The longer we work with a system, the more value we add. For legacy software, where institutional knowledge is often the biggest risk, that's the entire point.
Security-first engagement
ISO 27001 processes, mutual NDAs from day one, and experience in banking, telecom, and healthcare, industries where legacy systems and compliance requirements usually overlap.
Industries
Built for systems that can't be replaced overnight
Some systems can't be rebuilt without serious operational risk. These are the industries where that's most often true, and where testing has to work around decades of technical debt instead of ignoring it.
- Fintech & banking
- Healthcare
- Government & public sector
- Retail
- Insurance
- Telecom
- Manufacturing
- Travel and hospitality
Case studies
Trusted by companies in regulated industries where stakes are highest
Migrations create risk. So does losing the people who understood the system. Here's how we handled both, without either becoming a problem.
The challenge: After INDEXO's banking system launched, the company later migrated to new infrastructure, a change that risked introducing performance regressions into a live system.
TestDevLab re-ran the same load testing scenarios used before launch, confirming the migration hadn't degraded performance or introduced new issues.
INDEXO moved to new infrastructure with verified confidence.
The challenge: i-Hub's testing relied entirely on manual processes. When their existing manual test team later left the project, the risk wasn't just a testing gap, it was losing the accumulated knowledge of how the system actually behaved.
TestDevLab established the automation framework and documentation early in the project, ensuring knowledge was captured from the start. When the client’s QA team later transitioned, the project continued without interruption.
A testing process designed to outlast change.
FAQ
Questions people ask before getting started with legacy software testing
Yes, this is most of the job. Characterization testing captures what your system actually does today, using its real behavior as the specification, whether or not that behavior was ever written down.
No. Discovery, baseline testing, and coverage build-out are designed to run without disrupting the live system. Where a change does need a maintenance window, we scope that with you in advance, never as a surprise.
With risk, not everything at once. We map the highest-traffic and highest-revenue paths first, so the areas most likely to cause real damage are protected before anything else.
When standard tools don't reach a technology, we build a custom harness that does. Terminal emulation, desktop UI automation, protocol-level testing, this has been a specialty since 2011.
Behavioral parity testing: identical inputs run against both systems, with outputs compared automatically. Combined with data reconciliation and environment checks, so nothing quietly changes in the move.
Access is governed by mutual NDAs and ISO-certified processes from day one. Your code and data are handled by engineers under contract, within your existing security requirements.
That knowledge gets captured, not lost. Executable documentation and characterization tests record what the system actually does, so institutional knowledge outlives any one person's tenure.
Ready to test the system that's actually running your business?
Whether you're patching, integrating, or planning a full migration, we can map the risk before it becomes a problem.