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API Testing

What is an API?

Application Programming Interface (API) is a set of procedures and functions. It allows us to create an application by accessing the data or features of the operating system or platforms. 

What is API Testing?

API testing is a software testing practice that allows us to directly test the APIs to check the programming interfaces directly and as part of integration testing to determine if they meet expectations for functionality, reliability, performance, and security. API testing concentrates on the business logic layer in the software architecture, i.e., the middle layer between the presentation (UI) and database.

Benefits of API Testing

  • Test Early - With API testing, once the logic is designed, tests can be built to validate the correctness of responses and data. This eliminates the need to wait for the various team to finish their work or for complete applications to be made.  Since test cases are isolated, they are ready to be built immediately.

  • Easy Test Maintenance - Front-end software code is constantly changing. This creates challenging scenarios where tests are repeatedly rewritten to keep up with the code in production.  API changes are much more controlled and infrequent.  Often refactoring API tests can be done in short order. 

  • Improved Test Coverage - API tests are generally broad in scope. Defects often arise at the intersection where the scope of one-layer ends and the other begins. API-level tests are specifically designed to verify that all system components function as intended. API testing helps uncover potential defects in the interfaces, servers, and databases, thus improving overall software quality.

  • Time Efficiency - Automated API tests provide faster test results and significantly accelerate development workflows. API tests do not need to wait for the GUI to be ready and can be performed early in the agile development cycle. This helps speed up the feedback loop and catch issues faster. 

  • Reduced Costs - The cost-efficiency benefit of automated API tests leads to more effective resource consumption and lower overall testing costs. API tests can be performed as soon as the business logic is defined. And the earlier a bug is found, the less expensive it is to fix it. API testing enables the testing team to detect and resolve issues before they become a problem in production, keeping project costs at bay. 

  • Programming Language Independence - Automated API tests are application language independent. To be transferred over the Internet, data is exchanged in XML and JSON formats. Hence, engineers can use any programming language that supports technologies such as Java, Ruby, Python, PHP, etc.

Types of API Testing

  • Functional testing - a test of specific functions within the codebase.  These functions represent scenarios to ensure that the API functions within expected parameters and that errors are handled well when the results are outside the expected parameters.

  • UI testing - a test of the User Interface for your API and its integral parts. This test is specifically concerned with the function of the UI, whether that interface is graphical or depends upon command-line endpoint calls.

  • Load testing - checks the application’s ability to perform under anticipated user loads. The objective is to identify performance bottlenecks before the software application goes live.

  • Runtime/Error Detection - although the other API testing is concerned with implementing the API in an environment or scenario, this testing is chiefly concerned with the universal effects of utilising the API codebase.

  • Security testing - ensures the API implementation is secure from external threats. It includes validation of encryption methodologies, design of the API access control, user rights management, and authorisation validation.

  • Penetration testing - is a second step in the security auditing process. In this, the API is attacked by someone who has limited working knowledge of the API to assess the threat vector from an outside perspective. These attacks can be limited to certain functions, resources, processes or can target the entirety of the API and its constituent parts.

  • Fuzz testing - is another step in the security audit process. In fuzz testing, a vast amount of random data will be input into the system to detect any forced crashes or negative behaviours. This technique tests the API’s limits to prepare for the "worst-case scenarios."

  • Validation testing - occurs in the final steps of the development process. It verifies the aspects of product, behaviour, and efficiency.  Validation testing can be seen as an assurance of the correct development.

Automation of API Testing

API automated testing is critical for product quality and a successful CI/CD process.  API tests can cope well with short release cycles and frequent changes without breaking the test outputs.  Garnering the benefits of automated API testing is possible with a comprehensive tool for complete automation.

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