What is API testing, and How to Do it?

API (Application Programming Interface) testing is a type of integration testing performed to reveal bugs or other inconsistencies that affect the APIs' functionality, performance, and security. It is a daunting task as API testing can be challenging, especially when you aren't quite sure where to start. Developers may stick to testing mere basic functionality, but testers tend to check everything from functionality to reliability.

As we are already aware, consistent testing is essential to improve the effectiveness of your software as it validates the correctness of responses and data. Most applications consist of three layers called data, service and a presentation layer where the service and presentation layer translates to API and UI layer, respectively. Since the API layer deals with the business logic of software and touches both data and presentation layer, it is evident why API testing is a popular spot for QA (Quality Assurance) and development teams.

All app developers focus on the API development process as they do on API testing. APIs communicate endpoints and work as the intermediate that streamlines the data sharing process. This guide will provide an overview of API testing, its benefits and the best practices. It will also offer a comprehensive view of how to get started and perform API testing successfully.

An Overview of API Testing: Types and Benefits

An API enables the communication between two programs and is essentially known as the "middleman" or the middleware code. It gives value to applications and makes our phones "smart" by streamlining all processes. So if an API doesn't function well, it will never get adopted. For this reason, API testing is crucial to make sure APIs do what they're supposed to do, handle the load and ensure it works across devices, browsers and OSes. API testing evaluates an API to validate and verify its expected functionality by all terms.

Here are few benefits of API testing:

• They are language-independent, as any language can be used for test automation.
• They are GUI- independent as API testing can be done before GUI testing.
• They have improved test coverage.
• They allow development teams to release products faster.

The different types of API testing include:

• Validation testing: This type of testing verifies the expected behavior and efficiency of the product.
• Functional testing: It tests specific functionalities in the codebase.
• UI testing: The overall performance of the User Interface and the efficiency of the app's front and back ends are evaluated.
• Security testing: Security testing includes authorization validation and makes sure that apps are safe from external threats.
• Load testing: These tests monitor the app's performance and check if the theoretical solutions are working as expected.
• Runtime detection: This testing type offers an insight into the actual performance of the API by focusing on the monitoring, execution errors, resource leaks, etc.
• Penetration testing: This testing is done in the auditing process, where the prominence of external threats is assessed.
• Fuzz testing: Another type of security test done in the audit process. They detect forced crashes or negative behaviors.

Best API Testing Practices: How to Perform API Testing

Listed below are the essential steps that you can follow to perform API testing:

1. Documentation of API testing requirements: The first step is collecting all the API testing requirements such as the purpose of API, its workflow, features and finding out which integrations are supported by API. Documenting all these is an essential step when you are planning API tests.
2. Set up a testing environment: A testing environment is set up, where parameters selection is done in the test case itself. This process involves the configuration of the database and server.
3. Integration of application data: Here, we integrate your application data with API tests to ensure that it functions correctly.
4. Choose the API test type: After the initial setups and testing boundaries, you must choose what you want to test your API for. This could be any one of the different types of API testing mentioned above in the guide.
5. Execution and Reporting: After you complete all the four steps above, the next move would be to create test cases and then execute them. In the end, you may need to document the test results for later reference.

These are the best API test practices that any B2B ecommerce enterprise would perform to assess and evaluate different software programs. There are plenty of API testing tools such as SOAP, REST-assured, Katalon, Tricentis Tosca, Postman, to name a few. Though these tools come in handy when performing API tests, you may still face some challenges. However, regardless of these limitations, API testing is still crucial and almost indispensable.