Application Programmable Interface (API) enables communication and data exchange between two software systems. The software system may be an independent application in a monolithic architecture. For example – Integrating messaging application in another e-commerce application via API. The software system may be a microservice that communicate and data exchange with another microservice within an application in a microservices based architecture. For example – Integrating multiple software systems or microservices such as billing and ordering via API to build an e-commerce application. Please note once the same e-commerce application can also have another microservice in it that supports API to interact with or to integrate with any 3rd party application such as messaging application.
The API is the brain of our connected world that allows everything to work together in a streamlined and integrated way. Therefore, API testing is testing that API and the integration they enable work in the most optimal way. Not thoroughly testing API means it only break a single application but a chain of business processes hinged to it. API testing is entirely different from GUI testing. API testing mainly concentrates on the business logic layer of the software application while GUI testing focuses on the look and feel. Though GUI testing to some extent tests the business logic layer functionalities indirectly, it is not enough.
Testing application via API is must be covering tests from all aspects including characterizing the capacity and performance in the massive scale. Remember, not only through GUI the business logic is invoked but also through various 3rd party applications and internal microservices. So, in order to ensure the best quality and performance of an application, API testing must be done considering all aspects of integration and communication. API testing is complex and is one of the most challenging parts of the whole chain of software and QA testing. There are many variabilities that one must consider while developing test cases such as parameter combination, parameter selection, call sequencing, return value based on input conditions and trigger some other API/event/interrupt. The tester must understand the functionality of the API program and clearly define the scope of the program. Then, apply relevant testing techniques such as equivalence classes, boundary value analysis, and error guessing and write test cases for the API. Importantly, coding knowledge is necessary for testers. Although, some commercial tools try to avoid coding through different easy to use mechanism but may not cover all test possibilities.
TestOnNeed is an on-need QA test, automation, and DevOps expert trusted by industry-leading companies. We work with partners to create flawless, high quality, high-performance software application products. We enable continuous API testing of an application or microservices throughout the product development life cycle such as Discovery testing, usability testing, reliability testing, security testing, load testing, Documentation testing and more.
Conclusion: API enables integration and communication. If API is not tested properly, it may cause problems not only in one application or microservices but also in the calling application or microservices and eventually the whole business.
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