Testing APIs is an integral part of the testing process. Testing business logic pertains to the interaction between a user interface and underlying data and is part of the business layer. An API test pertains to a process of verifying the functionality, performance, and robustness of an API.
API’s change as business and functional requirements evolve, which makes testing them continuously even more critical. The fact that they must be tested as part of every release cycle makes them good candidates for automation testing. In addition to testing for functionality, API tests are also conducted to verify error conditions handling, response handling in terms of data and time, performance issues, and security issues. API testing is an essential aspect of testing business requirements, and to achieve good results, a number of best practices must be followed.
API Testing Dos
Classify Test Cases
It is not uncommon for an application to involve multiple APIs, the number of which may sometimes reach triple digits. It is beneficial to categorize the test cases so that they can be easily referred to and executed.
Prioritize API requests
In order to facilitate testing, API calls should be prioritized.
Automation of API testing
API tests are usually considered stable, and major changes are done mainly when the business logic changes. This makes them suitable for automated testing. API testing is a type of Black-box testing. It is also suitable for data-driven testing using a variety of combinations of inputs. Testing data, scripts, and API endpoints may be saved for future execution.
Select a suitable automation testing tool
Various tools, such as ParasoftSOATest, POSTMAN, Rest Assured, JMeter, Swagger, API Fortress, etc., are available in the market for API testing. To maximize the benefits of automation, choose a suitable tool carefully.
Create both positive and negative tests
To ensure a complete API test, it is necessary to run both positive and negative tests. Considering API testing is a data-driven process, one can test APIs using various combinations of data inputs. In both cases, it is important to ensure that APIs return appropriate responses to the calling function.
Share the test results
The failure of API testing should be brought to all stakeholders’ attention as soon as possible. Alternatively, in the event of a failure, immediate notifications could be sent through team notification channels. This will enable the team to respond promptly.
Perform load testing
APIs intended to perform load tests should either function as expected or fail gracefully in a predictable manner. The system must handle a variety of input data types and handle error conditions in the event of failure.
API Testing Don’ts
Ignore dependencies
APIs are frequently dependent on other APIs and sometimes on external services. The third-party APIs need to be tested in a test environment, and the dependent APIs need to be tested along with the third-party APIs to obtain a holistic picture. The entire ecosystem should be tested to ensure that any changes or upgrades made to other APIs do not adversely affect the functioning of other APIs dependent on them.
Missing assertions regarding response time
It is crucial to monitor the response times of API calls. Even though a test may pass functionally, there may be various reasons for the delayed response. This adversely impacts the end-user experience. Applications that take too long to compute, load, or provide results will not be used by the end-user. Therefore, it would be a good idea to include a time-based test to check response times. The API should be reported if it is taking too long to respond to investigate the code to determine the cause of the delay.
Treating security testing lightly
APIs, like any other code, are susceptible to threats and attacks. Conducting security tests becomes even more critical when a third-party API is used. Consequently, all possible loopholes must be tested and sealed.
