As discussed above, API testing is an important activity that testing teams should focus on. It offers a number of advantages over other kinds of testing:
- Language independent:
Data is exchanged via XML and JSON, so any language can be used for automation, independent from the languages used to develop the application. XML and JSON are typically structured data so the verification is fast and stable. There are also built-in libraries to support comparing data using these data formats.
- GUI independent
We can perform API testing within the application prior to GUI testing. Early testing will get feedback sooner and improve the team’s productivity.
Core functionality can be tested to expose small errors and to evaluate a build’s strengths.
- Improved test coverage
Most API/services have specifications, allowing us to create automated tests with high coverage, including functional testing (happy cases, negative cases) and non-functional testing. With virtual user techniques, we rarely find API test cases that could not be automated.
- Faster releases
It is common that executing a UI regression test suite takes 8-10 hrs while the same scenario with API testing takes only 1-2 hours. The flakiness of API testing is also lower than that of UI testing. All these allow us to release faster with API testing.