What is API testing?
Application Programming Interface (API) testing is a sort of software testing that examines APIs, or application programming interfaces. These testing services attest to the accuracy, functionality, security, and dependability of an application. When running test cases with the aid of API testing tools, QA teams gain from API automation. You utilise software to submit requests to the API, retrieve output, and record the system's answer rather than utilising typical user inputs (the keyboard) and outputs. API tests are considerably different from Graphical interface tests in that they don't focus on how an application appears and feels. It focuses mostly on the software's business logic layer.
What does it have to do with UI testing then?
The advantages of API testing centre on the business logic layer of the software's design, whereas UI testing concentrates on the appearance and feel of the user interface. In other words, API testing has an advantage over UI testing in that it can verify an API's validity from all perspectives aside from how the user interacts with the software application.
Why API testing is necessary?
APIs are responsible for interaction between applications, allowing them to access data and create gateways for interacting with external systems. This is why, if there’s a slow API, it can impact all other integrations. For example, a slow third-party payment API can slow down the transaction process. Therefore, APIs must meet the benchmark to avoid such issues.
API testing environment setup
An application that can be used with an API is necessary for testing. An API must be tested to:
• Drive the API using the testing tool.
• Develop your own code to evaluate the API.
Points to note:
• In contrast to other software testing kinds, API testing requires you to build up an initial environment that invokes API with a specific set of parameters before examining the test result.
• As a result, creating a testing environment for API automation testing appears to be somewhat difficult.
• The database and server should be set up in accordance with the needs of the application.
• The API Function must be called after the installation is complete to verify that the API is operational.
Test Plans for API Evaluation:
• Returns based on input conditions: Given that input can be described, and results can be verified, returning a value based on an input condition is comparatively simple to verify.
• Does not produce a return: When there is no return value, the system's API behaviour needs to be examined.
• Trigger another API, an event, or an interruption: If an API output causes an event or an interruption, those events and interrupt listeners should be monitored.
• Update data structure: Any outcome or impact on the system from updating the data structure needs to be verified.
• Modify specific resources: If an API call modifies any resources, the modification should be verified by gaining access to the relevant resources.
API Testing Methodology
The QA team will use the API Testing Approach, a predetermined strategy or approach, to carry out API testing once the build is complete. The source code is not tested in this testing. The API testing strategy aids in a better understanding of features, testing methods, input parameters, and test case execution.
The user can perform an API Testing strategy by keeping in mind the following:
• Understanding the API program's functionality and defining the program's scope precisely
• Create test cases for the API using testing approaches like equivalence classes, boundary value analysis, and error guessing.
• The API's input parameters must be thoughtfully considered and described.
• After the test cases have been executed, compare the projected and actual results.
Tools for API testing
Developers have two options when doing an API test: they can create their own framework or select from a variety of ready-to-use API testing solutions. Because they are not constrained by the features of a particular tool and its plugins, developers can customise the test by creating an API test framework. To their chosen coding platform, testers can add any libraries they deem acceptable, create their own, practical reporting criteria, and include intricate logic in their tests. However, if they decide to create their own framework, testers will need extensive coding abilities.
API testing tools come in a variety of forms, from free downloads to high-end subscription services. Several examples of API testing tools are as follows:
• Apache JMeter
• REST Assured
• Swagger UI
In conclusion, API testing is crucial to every application. If it is not thoroughly tested, invoking the application may result in issues. It is an essential and required test in the lifetime of software.