
Language-independent
Data is exchanged via XML and JSON formats, so any language can be used for test automation. XML and JSON are typically structured data, making the verification fast and stable. There are also built-in libraries to support comparing data using these data formats.
GUI-independent
API testing can be performed in the app prior to GUI testing. Early testing means early feedback and better team productivity. The app's core functionalities can be tested to expose small errors and to evaluate the build's strengths.
Improved test coverage
Most API/web services have specifications, allowing you to create automated tests with high coverage — including functional testing and non-functional testing
Faster releases
It is common that executing API testing saves up to eight hours compared to UI testing, allowing software development teams to release products faster.