SoapUI
SoapUI is a desktop API testing tool for functional, regression, and load testing of both SOAP/XML web services and modern REST/JSON APIs — one of the few widely-used tools that still gives SOAP-based testing first-class support, which matters for teams integrating with older enterprise systems (many banking and government systems, including some in Nigeria, still expose SOAP interfaces alongside or instead of REST). Tests are built visually by defining requests, assertions on response content/status/timing, and property transfers that chain data between requests in a test suite.
The free open-source edition covers functional testing, mock services (useful for testing against an API that doesn't exist yet or is unavailable), and basic load testing. SoapUI Pro (commercial, via SmartBear) adds data-driven testing from CSV/Excel/databases, security testing scans, and CI/CD integration for automated pipeline execution.
For Nigerian fintech and enterprise integration teams that need to validate both a modern REST payment API and a legacy SOAP core-banking interface from the same tool, SoapUI's dual protocol support is a practical advantage over REST-only tools like Postman, though most teams doing REST-only testing today reach for Postman or Insomnia instead for their friendlier UI.