FAQ

Working with legacy applications is one of those tasks that almost every developer or QA team will face at some point. These systems often lack proper documentation, have fragile dependencies, and usually come with years of “quick fixes” piled on top of one another. Yet, businesses rely heavily on them, which makes testing critical. That’s where functional test cases become the anchor for stability.

The first step in creating functional test cases for legacy applications is understanding the business logic. Since technical documentation is often missing or outdated, collaborating with business stakeholders becomes key. Ask questions like: What must absolutely not break? Which features are business-critical? These insights help prioritize which test cases to write first.

Another common challenge is identifying test scenarios when the system is too complex. A good approach is to start with the most frequently used user workflows. By validating these workflows with functional test cases, you create an immediate safety net. Over time, you can expand to edge cases and less-used features.

Automation also plays an important role here. Legacy systems are notorious for introducing regressions when updated. By gradually automating functional test cases, teams can save time and reduce the risk of recurring bugs.

This is where tools like Keploy can make life easier. Instead of writing every test case from scratch, Keploy captures real API traffic from the legacy system and automatically generates test cases and mocks. This not only accelerates coverage but also ensures your tests are grounded in real-world usage, making them far more reliable.

In short, when dealing with legacy applications, start small, focus on business value, and lean on functional test cases as your guiding light. With the right approach and tools, even the oldest systems can be tested with confidence.