Testing Guides

What is API Testing?

Published on
October 19, 2022
Sneha Christall
Product Marketing Manager

This guide provides an overview of API testing, API test automation methodologies, types of API testing, benefits, and challenges, as well as API testing best practices.

API Testing- An Overview

Earlier, we discussed API testing in our blog on Test Automation 101. In a nutshell, the Application Programming Interface (API) connects the front end of your site to your back end using business logic. This means that the API determines how data is created, stored, and changed as well as who can access it. 

As compared to Functional User Interface (UI) testing, which focuses on the application's look, feel, and functionality, API testing focuses on analyzing the application's business logic as well as security and data responses (for example, client account access versus admin account access). An API test is generally performed by making requests to one or more API endpoints and comparing the responses with expected results. The tests are performed either directly on the API or as part of integration testing

You can also combine API testing with Functional UI testing to get a truer reflection of your end users' experience. The advantages of this type of testing are cross-checking front-end UI logic with the back-end and optimizing permutations and combinations with a UI setup and API execution.

What is API Test Automation?

API test automation is the process of automating the testing of Application Programming Interfaces or APIs. It is frequently automated by QA and DevOps teams to ensure that continuous testing is followed. It helps ensure that APIs perform as intended and are secure from potential vulnerabilities. In the long run, this helps save both time and money.

API Test Automation Process

An API test automation process should have a clearly defined scope with objectives relating to API functionality, endpoints for testing, and response codes for successful and unsuccessful requests, as well as error messages in the case of unsuccessful requests. 

With these indicators clearly defined, testers can begin the process of developing test cases to analyze factors such as data quality, response time, authorization confirmation, and error codes. In this manner, the API test automation process accounts for multiple endpoints across web services, databases, and web UIs. 

Testers must pick the ideal API test automation tool that ensures the API can handle the expected user load and work across multiple browsers and devices while boosting system performance and security.

Types of API Testing

  1. Validation Testing: Validation testing occurs towards the end of the development process and it helps ensure product efficiency and behavior. 
  2. Functional Testing: In functional testing, specific functions in the codebase are tested to ensure that the API functions are operating correctly within set parameters. 
  3. Security Testing: Security testing ensures that the API is safeguarded from external threats and vulnerabilities. It also considers aspects of authorization validation and user rights management. 
  4. Load Testing: Load testing is performed to validate the app’s performance in both normal and peak conditions. 
  5. UI Testing: UI testing focuses on the interface that is associated with the API and helps provide insights into the app’s health, usability, and functionality. 
  6. Runtime and Error Detection: Here, the testing emphasis is on aspects related to monitoring, execution errors, resource leaks, and error detection.
  7. Penetration Testing: In penetration testing, testers attempt to identify external threats relating to functions, resources, and processes relating to the entire API. 
  8. Fuzz Testing: In fuzz testing, a large and random dataset is input into the system to check for crashes or other undesirable behaviors. This helps prepare the app for worst-case scenarios. 

Benefits of API Testing

API testing enables the testing process to begin early on in the software development life cycle, even before the UI is ready. This helps quash bugs before they cause more serious errors while helping expose security threats. As continuous testing demands instant feedback, API tests help in this regard– they are efficient, can manage shorter release cycles without breaking test outputs, and guarantee that the connections between platforms are reliable and scalable. Below are a few of the benefits of API testing:

  1. Quality Assurance: Due to the constant feedback mechanism that is intrinsic to API testing, businesses are better positioned to garner customer trust and satisfaction. 
  2. Early Defect Detection and Resolution: As API testing employs a shift-left approach, testers are enabled to identify defects sooner, making the development process more stable and predictable. 
  3. Automatic Validation: With rapid iterations, testers can execute their API tests within CI/CD pipelines, automatically validating every code change before it reaches production.
  4. More Focus on Innovation: While API testing becomes more and more automated, this saves up the team’s time to focus on new innovation. 
  5. Improved Test Coverage and Maintenance: As changes to APIs are relatively less frequent than UI changes, it helps to reduce the constant refactoring of tests. 
  6. Shorter Time to Resolution: As API test failures are easy to track and identify, the defect can be easily managed and fixed, reducing time to resolution and allowing software development teams to release faster. 

Challenges of API Testing

 Listed below are a few common challenges to API testing:

  • Validating and verifying outputs in a different system is a challenging process.
  • Parameter selection requires the parameters sent through API requests to be validated– once again, a process that can be quite challenging. 
  • The exception-handling function needs to be tested.
  • Coding knowledge is mandatory for testers.
  • There are no GUIs available to test the application, making it more challenging to provide input values.
  • Each API may work when tested independently, but not when testing the entire application.

API Testing Best Practices

  • Test for typical or expected results first.
  • Add stress to the system through a series of API load tests.
  • Automate API tests where possible to further systematize the approach. 
  • Run API tests at every stage of the API lifecycle. 
  • Develop distinct, organized test suites for each API resource. 
  • For optimal test coverage, develop test cases for all possible API input combinations.
  • Create reusable tests wherever possible to reduce occurrences of human error and improve consistency in endpoint testing. 
  • Prioritize API function calls to ease the burden of testers.

How Virtuoso Enables API Testing?

If you are interested to learn how Virtuoso enables API test automation, read our product documentation here or watch our 60-second video here.

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