The Definitive Guide to API Testing Tools

Code Mastery Centre

19 Oct, 2023

In today's interconnected digital landscape, the importance of API testing cannot be overstated. The seamless operation of the services we rely on daily hinges on the proper functioning of multiple interconnected APIs. A glitch in any of these APIs can compromise the entire service.

To ensure that everything runs smoothly, it is crucial to employ the best API testing tools available. In this comprehensive guide, we will introduce you to the top six API testing tools, but before that, let's dive into the fundamentals: what exactly is an API, and why is API testing essential?

What is an API?

APIs (Application Programming Interfaces) serve as the linchpin that allows different software applications to communicate and interact with one another.

They establish precise rules and protocols governing the types of requests an application can make, the data format in which these requests should be made, and the practices users must adhere to.

Here's how it works: When an application connected to the internet sends a request with data to a server, the server receives and interprets the request. Once the necessary actions are performed, the server sends a response back to the application's user interface, providing the requested information.

What is API Testing?

API testing is the process of evaluating whether APIs have been developed correctly. It involves analyzing whether APIs fulfil their intended purpose to ensure the application's functionality, reliability, security, and performance remain uncompromised.

API testing typically involves testing SOAP web services or REST APIs, using JSON or XML message payloads, which are transmitted through various protocols such as HTTPS, HTTP, MQ, and JMS.

API testing tools empower testers to scrutinize several crucial aspects, including:

Response Verification: Confirm whether an API returns the expected response in the correct format.
Handling Edge Cases: Ensuring that the API responds appropriately to failures and unexpected inputs.
Security Checks: Validating that the API can withstand potential security threats.
Response Time: Evaluating the time it takes for an API to deliver a response.

The Best API Testing Tools

Now that you have a clear understanding of what APIs are and why API testing is vital, let's delve into the top API testing tools that can supercharge your testing efforts.

1. Apigee

Apigee is a cross-cloud API testing software that operates on JavaScript. It offers developers and testers a powerful platform to access its features through different editors. Apigee excels in handling large amounts of data, making it ideal for robust and complex digital businesses.

It can identify performance bottlenecks by analyzing API traffic, response times, and potential error rates. Apigee also enables the creation of proxies from Open API Specification.

The tool provides a free trial, allowing you to evaluate its capabilities before making a commitment. Following the trial, you can choose from different packages, including Evaluation, Standard, Enterprise, and Enterprise Plus.

2. SoapUI

SoapUI is a dedicated API testing tool that specializes in testing SOAP APIs and REST web services. Known for its robustness, it allows testers to create complex scenarios and supports asynchronous testing. With features like data-driven testing and user-friendly interfaces, SoapUI is a preferred choice for many.

SoapUI offers both free and pro packages. The free version is straightforward to use and allows script reuse. The pro package offers advanced features like custom code creation, data extraction from various sources, and native CI/CD integrations.

3. Katalon

Katalon is a versatile test automation tool for APIs, web applications, and mobile apps. It supports SOAP and REST requests, provides numerous parameterization features and commands, and follows a data-driven approach. Even non-technical users will find it user-friendly.

Katalon offers a robust free package. For more extended features and private plugins, you can opt for the Studio Enterprise package. There's also a Runtime Engine package for executing tests in CI/CD pipelines or via the command-line interface.

4. Postman

Postman is an excellent tool for testing API services, including monitoring, debugging, and running requests. It's compatible with various formats like Swagger and RAML and doesn't require users to learn a new programming language. Postman offers a user-friendly interface, workspaces, and collections.

Postman is free for basic use. If you need additional features, there's a paid version priced at $12 per month per user.

5. Tricentis

Tricentis is a top choice for organizations looking to integrate API testing into the Agile and DevOps cycles. It employs a model-based test automation approach, making script maintenance easier and enabling fast regression testing. Tricentis supports multiple protocols, such as REST, SOAP, HTTP(s), MQ, JMS, NET TCP, IBM MQ, and more. It also allows end-to-end testing across various platforms.

The pricing for Tricentis may vary depending on your specific requirements.

6. Assertible

Assertible is renowned for its focus on reliability. It supports API testing at every stage, from continuous integration to the delivery pipeline. Assertible offers valuable features such as integration with GitHub, Zapier, and Slack, as well as HTTP response validation with turnkey assertions.

The tool offers three different packages: Standard, Startup, and Business. The pricing varies, and there's also a free personal plan for smaller-scale API testing.

Conclusion

Choosing the right API testing tool is crucial for ensuring the smooth operation of your applications. Different tools cater to various needs, so it's essential to prioritize the features that matter most to your organization or project.

While all the API testing tools mentioned in this guide have excellent reputations, the best tool for you will be the one that aligns most closely with your specific requirements.

If you've found this guide useful, you may also be interested in exploring our other articles on topics such as Developers Tools, Learn Code, and more. At Code Mastery Centre, we're dedicated to simplifying complex systems and delivering user-friendly interfaces.