API Testing Tools: Best 15 Reviewed

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Your app is only as strong as the APIs it depends on. When you’re designing, developing, and maintaining APIs within a CI/CD pipeline, one untested endpoint can break everything. In this environment, one constant remains: the need for effective and efficient testing.

API testing has become a cornerstone in this process; it enables the seamless integration and functionality of software applications. So more than a best practice, it’s essential for delivering reliable, high-performing software.

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What is an API Testing Tool?

APIs, or Application Programming Interfaces, serve as the building blocks of software applications. An API testing tool is software that tests application programming interfaces (APIs) for functionality, performance, security, and reliability, often by validating aspects such as status codes, custom headers, and response formats. It checks that APIs meet expected standards and work correctly with other software components.

API Testing Tools can help us to automate the process of validating the performance, reliability, and functionality of APIs. By automating these tests, we can increase efficiency, reduce errors, and accelerate the delivery of high-quality software.

Benefits of API Testing

API testing is a crucial aspect of software testing that offers numerous benefits to developers, testers, and organizations. Here are some of the key benefits:

Improved Accuracy

API testing helps ensure that APIs function correctly and return the expected results, reducing the likelihood of errors and bugs. This accuracy is vital for maintaining the integrity of software applications.

Increased Speed

By automating the testing process, API testing allows developers to test APIs quickly and efficiently. This reduces the time and effort required for manual testing, accelerating the overall development cycle.

Better Teamwork

API testing fosters better collaboration between developers and testers. It validates if APIs meet the required standards and functionality, promoting a more cohesive and efficient development process.

Stronger and More Reliable Software

Confirming that APIs are robust, reliable, and secure is a key outcome of API testing. This reduces the risk of errors and bugs that can impact the overall quality of the software. Maintaining API quality throughout the development lifecycle helps teams deliver reliable software.

Faster Release Process

With the ability to test APIs quickly and efficiently, API testing enables faster release cycles. This allows organizations to bring their products to market more swiftly, staying ahead of the competition.

Choosing the Right API Testing Tool

Selecting the right API testing tool is crucial for effective and efficient API testing. Here are some factors to consider when choosing an API testing tool:

• Ease of Use: Opt for a tool that is user-friendly and easy to navigate, even for non-technical users. A simple interface can significantly reduce the learning curve and increase productivity.
  
• Scalability: Check if the tool can handle large volumes of API traffic and scale to meet the growing needs of your organization. Scalability is essential for maintaining performance under varying loads.
  
• Customization Options: CChoose a tool that offers customization options to tailor the testing process to your specific needs, such as defining unique parameter values or adjusting to multiple environments. This flexibility can help address unique testing requirements and scenarios.
  
• Integration with Other Tools and Systems: Select a tool that integrates seamlessly with other tools and systems, such as CI/CD pipelines and testing frameworks. This integration is vital for maintaining a smooth and efficient workflow.
  
• Support and Documentation: Comprehensive support and documentation are essential for getting the most out of the tool. Verify if the tool provides adequate resources to help you troubleshoot issues and maximize its capabilities.

With the right tool, you can strive for your APIs to function as expected, meet performance standards, and deliver a seamless user experience.

At Abstracta, we understand that effective testing strategies go beyond just tools. We offer holistic testing services that encompass not only state-of-the-art tools but also strategic planning and partnership. Partnering with us means gaining access to a wealth of expertise and top-tier testing tools to empower your teams, boost your quality, and accelerate your time to market.

Having reviewed de basics, let’s explore our pick of the top API testing tools!

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Overview Of The 15 Best API Testing Tools

When comparing API testing tools, we consider several factors. These include ease of use, functionality, performance, and more. Ready to dive in? Let’s get started!

1. Postman

Launched in 2012, Postman revolutionizes API testing by providing an intuitive platform for creating, sharing, testing, and documenting APIs. It’s designed to simplify web services testing, making it a staple in modern API development with features that enhance collaboration, streamline automation, and offer seamless integration with CI/CD pipelines.

Benefits:

• User-Friendly Interface: The intuitive UI of Postman simplifies the API testing process, making it accessible for users of all skill levels. Its free version is ideal for individuals or small teams starting out with API testing.
• Enhanced Collaboration: Encourages team collaboration in API development through shared workspaces and collections, promoting a more cohesive workflow.
• Robust Automation: Supports comprehensive automated testing with features for running collections and inspecting results, streamlining the testing process.
• Seamless Integration: Integrates with CI/CD pipelines, facilitating continuous testing and efficient workflow integration.
• Customizability and Extensibility: Allows users to tailor their experience with options to add integrations, write custom test cases, and create mock servers, making it a versatile tool for a wide range of testing needs.. This enhances the flexibility and scope of API testing.

2. SoapUI

Founded in 2005 by SmartBear Software, SoapUI is an open-source tool acclaimed for its comprehensive support in automated functional, regression, compliance, and load testing of both REST and SOAP APIs, fostering a collaborative and flexible testing environment

Benefits:

• Functional testing: It offers comprehensive support for testing all aspects of REST and SOAP APIs.
• Load testing: With SoapUI Pro, you can quickly create and run load tests.
• Security testing: It allows you to perform detailed security tests. It verifies if your APIs are safe from common vulnerabilities.
• Scripting: It offers powerful data-driven testing. It allows you to run tests with varying input data.
• Open Source: The community can freely access SoapUI. This drives enhancements and solves problems together.

Don’t miss this article! API Testing with SoapUI and Postman

3. Testsigma

Testsigma is where AI meets API, web, and mobile application testing. It’s designed to make the testing process smoother and more intuitive, bridging gaps between development and quality assurance.

Benefits:

• AI-Driven Efficiency: Accelerates the API testing process through intelligent automation.
• Real-Time API Validation: Provides immediate feedback on API performance.
• Data-Driven Testing: Enhances test coverage by using varied test data sets.
• CI/CD Pipeline Integration: Supports continuous testing in development pipelines.
• Chained API Testing: Offers comprehensive coverage through interconnected API tests.
• Codeless Test Creation: Codeless Test Creation: Enables easy test creation without requiring programming skills, making it accessible for other roles beyond test engineers across different teams.
• Support for Multiple API Methods: Accommodates various API request types.

4. Katalon Studio

Katalon Studio integrates AI to enhance both the functional and aesthetic aspects of APIs. It’s recognized for its ability to bring efficiency and beauty to API user interfaces.

Benefits:

• IDE for API Automation: It streamlines API testing with an IDE that boosts efficiency in scripting, debugging, and maintenance through advanced features like autocompletion, code inspection, and a dual interface.
• API-Centric Testing Solution: It provides comprehensive support for REST, SOAP/1.1, SOAP/1.2 requests, and easy test import from Swagger, Postman, and WSDL.
• Compatibility with Modern Frameworks: It leverages data-driven testing with support for multiple data sources and databases, along with compatibility with BDD and native Gherkin editor, aligning with modern testing frameworks.
• Sustainable and Scalable Testing Platform: It enhances CI and DevOps practices with an IDE offering built-in integrations, easy deployment through Docker, and scalable testing with local and remote execution capabilities.
• Minimal Maintenance Effort: It reduces maintenance work and improves efficiency with the ability to reuse test artifacts across projects and manage complex test scenarios effectively through comprehensive test suite management.

5. mabl

Think of mabl as the approachable expert in AI-driven, low-code integrated API testing. Since 2017, it has been making end-to-end testing a breeze, especially for web applications. It’s like having a helpful guide by your side, simplifying complex testing tasks.

Benefits

• Postman Compatible: It allows to quickly import Postman Collections and utilize unlimited parallel test runs for efficient test orchestration.
• Low-code API Testing: It simplifies API testing for users of any skill level with a low-code solution that supports data-driven testing and variable management.
• Unified Platform: It enables comprehensive end-to-end (E2E) test coverage by merging UI and API tests, with centralized reporting for a complete overview of functional test coverage.

Would you like to know about mabl? We invite you to read this article: Mabl Review: First Steps With The Low-Code Test Automation Solution

6. Sauce Labs API Testing

Sauce Labs provides a comprehensive tool that helps teams streamline API performance from start to finish. It enables users to create and execute tests, generate load tests, virtualize APIs, and monitor live APIs.

Benefits:

• Functional API Testing and Monitoring: Elevate the efficiency and scalability of functional, business logic, and data-driven API testing with automation features. This includes an onboard test scheduler, integrations with CI/CD platforms and event management tools like PagerDuty, and validation against the expected API schema to detect inconsistencies early.
• Integration Testing: Quickly create and execute fast and accurate API integration tests with Sauce Labs, which allows for effective collaboration and reusability of tests, variables, and environments for comprehensive end-to-end validations.
• Contract Testing with Mocking: Sauce Labs streamlines API development by allowing the importation of OpenAPI specification files to generate contract tests. The goal is to enable compliance and the ability to extend tests with functional elements.
• Load Testing & API Benchmarking: Improve API performance insights during development by reusing functional tests as load tests. Simulate realistic traffic patterns, compare benchmarks across environments, and identify performance bottlenecks early in the lifecycle.

7. Apigee

Now part of Google Cloud, Apigee is a full lifecycle API management platform. It enables API providers to design, secure, deploy, monitor, and scale APIs. Founded in 2004 and acquired by Google in 2016, it provides a platform for developing and managing APIs. It has a range of capabilities, which include API design, API analytics, developer portal, and API security.

Benefits:

• Simplified API Development: Apigee offers tools and services to streamline API creation, testing, and debugging​​.
• Enhanced API Security: It provides advanced security features for APIs, including authentication, authorization, and encryption, to protect data and foster secure testing​​.
• Scalable API Management: Apigee allows for efficient management of APIs at scale, with features like API versioning and rate limiting that are crucial for high traffic conditions​​.
• Real-Time Monitoring and Analytics: The platform enables real-time tracking of API performance, which is essential for effective testing and optimization​​.
• Debugging and Diagnostic Tools: Apigee’s UI and API tools offer in-depth diagnostic capabilities to trace and debug API requests, aiding in the testing process​​.
• API Lifecycle Management: Apigee supports the full lifecycle of APIs, from development to deployment, testing, and retirement, making it a comprehensive tool for API testing​​.
• Developer Portal Accessibility: The platform includes a developer portal that aids in discovering and understanding APIs, which is beneficial for API testing phases​​.
• Hybrid and Multi-Cloud Deployment: It supports deployment across various environments, including private and public clouds, SaaS, and on-premises, providing flexibility in API testing​​.
• Integration with Google Cloud: Apigee integrates seamlessly with Google Cloud Services, offering enhanced capabilities for building, deploying, and scaling APIs within the Google ecosystem​​.
• API Proxy-Based Architecture: Apigee enables testing and management through an API proxy-based model, which decouples backend services from the API consumer and adds a layer of security, monitoring, and control.

8. Karate DSL

It is an open-source tool for API testing that combines API test automation, mocks, performance testing, and even UI automation into a single, unified framework. Released by Intuit in 2017, its main purpose is to simplify the process of creating complex API tests, performance tests, and creating mock services.

Benefits:

• Simplicity: Karate DSL requires no Java knowledge. This makes it easy for non-programmers to create and manage tests.
• Flexibility: It allows testers to reuse payload data and user-defined functions across tests.
• Performance Testing: Karate DSL integrates with Gatling for performance testing. This allows you to reuse your functional tests as performance tests.
• Mocking: It provides a built-in capability to set up mock services. This can be used to test edge cases and error conditions. Additionally, it supports behavior-driven development, which helps define tests clearly and understandably for all stakeholders.

9. GoRest

Introduced in 2018, GoRest serves as an efficient platform for those eager to explore and test RESTful APIs. It’s a tool that balances learning and professional API testing.

Benefits:

• Learning Tool: GoRest is an excellent tool for those learning about a restful API service and how to consume it.
• Testing: It provides a variety of endpoints for users to test different types of requests, including GET, POST, PUT, PATCH, and DELETE.
• Data Variety: GoRest provides a variety of data types for users to work with, including users, posts, comments, and more.
• Free to Use: GoRest is free to use, making it accessible for anyone wanting to learn or test RESTful APIs.

10. Rest Assured

Rest Assured is an open-source Java library that simplifies the testing and validation of REST APIs by providing a domain-specific language (DSL) for writing tests. Released by Jayway in 2010 (now a part of Tricentis), it is used for testing and validating REST services in Java.

Benefits:

• Simplicity: Rest Assured provides a simple, user-friendly interface for sending HTTP requests and verifying HTTP responses.
• Integration: It integrates seamlessly with existing Java-based testing ecosystems, making it an excellent choice for Java application testing scenarios. These include JUnit and TestNG.
• Flexibility: It supports XML and JSON request/response payloads. Teams can use it to test REST services implemented in any language.
• Authentication: It supports various methods of authentication. These include Basic, Digest, Form, and OAuth.

11. k6

k6 is a cutting-edge, open-source performance testing tool. It is used to test the scalability, reliability, and performance of software systems, most commonly web services. Unlike GUI-based testing tools, K6 emphasizes scriptability, automation, and integrations into development workflows.

Benefits:

• Open Source: The community can freely access K6. This drives enhancements and solves problems together.
• Scriptable: Developers write API tests in JavaScript, and can simulate interactions using CSV files to generate dynamic datasets. This provides flexibility and the option to incorporate modules and external libraries.
• Modern Architecture: K6 suits modern cloud-native architectures. It easily integrates with DevOps workflows.
• CLI-Based: K6’s command-line nature enhances its automation potential. This makes it a prime choice for continuous integration pipelines.
• Extensible: Users can expand K6 and connect it with other platforms. These include Grafana and InfluxDB. This allows them to delve deeper into visualization and analysis.

12. JMeter

Apache JMeter is an open-source software designed to load test functional behavior and measure performance. It was originally designed for testing Web Applications but has since expanded to other test functions.

Find out How to Automate API Testing Using JMeter?

Benefits:

• Multi-protocol Support: JMeter supports testing for several protocols. These include HTTP, SOAP, JDBC, LDAP, and JMS.
• Platform-independent: Being a Java desktop application, it can run on any system that supports Java.
• Multi-threading Framework: This allows concurrent and simultaneous sampling of different functions by many separate threads. It also allows simultaneous sampling of the same function by separate thread groups.
• Visualization: It provides a variety of graphical analyses of performance reports.

While powerful and flexible, JMeter may present a steep learning curve for beginners due to its interface and extensive configuration options.

Check out this article! JMeter DSL, an Innovative Tool for Performance Testing.

13. BlazeMeter

BlazeMeter is a powerhouse in performance and load testing, becoming a vital tool for API testing. It stands out for its ability to simulate a wide range of user scenarios, making it a top choice for assessing API performance under varied conditions.

Benefits:

• Scalable Performance Testing: Scalable Performance Testing: Offers robust capabilities for testing APIs under heavy load, including support for open API specifications to streamline test configuration.
• Realistic User Scenarios: Simulates real-world user scenarios for more accurate testing results.
• CI/CD Integration: Seamlessly integrates with continuous integration and delivery pipelines, enhancing development workflows.
• Comprehensive Reporting: Provides detailed performance insights, helping teams make informed decisions.
• Flexibility and Ease of Use: Offers a user-friendly interface and flexible configuration options, catering to both novice and experienced testers.

14. Paw

Paw, designed specifically for Mac users, is a comprehensive tool for API development and testing. It’s renowned for its robust environment that caters to building, exploring, and automating API tests.

Benefits

• Intuitive Design Interface: Streamlines the process of API request construction and response analysis.
• Automation Capabilities: Facilitates the automation of API tests, enabling developers to efficiently validate API responses and behavior.
• Dynamic Values: Offers dynamic values and test scripts for a more flexible and powerful testing experience.
• Comprehensive Documentation: Generates detailed API documentation, aiding in collaboration and knowledge sharing.
• Extensive Integration: Supports integration with various tools and services, enhancing its utility beyond just API testing.

15. Insomnia

Primarily known as a manual API testing client, Insomnia also offers features that extend into the realm of API automation. Insomnia supports configuring and creating query parameters for dynamic and complex requests. Its ability to run tests and validate responses makes it a valuable tool for developers seeking a versatile API client.

Benefits

• Easy-to-Use Interface: Simplifies the creation and execution of API requests.
• Test Running and Validation: Enables automated test runs and response validations, important for consistent API testing.
• Environment Management: Manages different environments and variables, streamlining the testing process across various conditions.
• Plugin Support: Offers extensibility through plugins, enhancing its functionality.
• Rich Response Viewing: Provides detailed views of API responses, aiding in thorough analysis and debugging.

We invite you to keep learning about Insomnia in this review.

The Future of API Testing Tools

We are witnessing a time when API testing tools are becoming increasingly intelligent and integrated. Drawing from our experience, we know that they will increasingly offer more advanced features, pushing the boundaries of what is currently possible.

These advancements include AI-powered testing applications, providing unprecedented accuracy and efficiency. They also feature real-time API monitoring for instant feedback and rapid issue resolution, and cross-cloud testing to enable consistent performance across multiple cloud platforms.

One clear example of this is already between us; it’s Abstracta Copilot, our new AI-powered assistant that speeds up API testing by 40% by enabling connection to APIs using natural language.

By bridging the technical skills gap, you can access databases without SQL knowledge, interface with APIs without specialized tools like Postman, and manage mainframes seamlessly—all without the need for expert-level skills.

In addition to these advancements, we also anticipate the emergence of new API testing tools bringing fresh perspectives and innovative approaches to automated API testing, further expanding the range of options available to testing teams. Moreover, we expect these tools to become more accessible, making it easier for teams of all sizes and skill levels to leverage the power of API testing.

In conclusion, API testing tools are set to play an even more critical role in software development. As they continue to evolve and as other API testing tools enter the scene, they will provide invaluable support to testing teams. They will drive efficiency, enhance quality, and foster innovation.

FAQs about API Testing Tools

What Is API Testing?

API testing involves testing application programming interfaces (APIs) for functionality, performance, security, and reliability. It checks that APIs meet expected standards and work correctly with other software components.

How Do I Start Testing APIs and What Tools Are Available?

To start testing APIs, beginners often choose intuitive platforms like Postman or Insomnia. These tools simplify the process of creating requests, handling creating query parameters, and inspecting responses. Many of them support testing across all your APIs, regardless of the provider or protocol (REST, SOAP, GraphQL). For more flexibility, some also allow configuring custom headers and working with data-driven scenarios.

Which Tool Is Used for API Testing?

Postman, SoapUI, Testsigma, Katalon Studio, mabl, Sauce Labs API Testing, Apigee, Karate DSL, GoRest, Rest Assured, k6, JMeter, BlazeMeter, Paw, and Insomnia are some popular tools for API testing. For teams seeking a proprietary tool with advanced AI support, Abstracta Copilot offers enhanced efficiency.

What Are the Best Open Source API Testing Tools?

Tools like SoapUI, JMeter, Rest Assured, Karate DSL, and k6 are widely used for open-source API testing. They offer active development, extensive documentation, and vibrant forums, providing strong community support that helps teams learn, troubleshoot, and evolve their testing practices efficiently.

What Are The 3 Types of Testing in API?

1. Functional Testing: Validates the functionality of the API and its responses.
2. Performance Testing: Assesses the API’s performance under various conditions.
3. Security Testing: Evaluates the security aspects of the API, including authentication and authorization.

These are the most popular types of API testing frequently asked about. However, there are plenty of them. Some examples include load testing, runtime testing, and interoperability testing, among others. We invite you to read this article: API Performance Testing and Load Testing Essentials

Do API Testing Tools Support Different Programming Languages and Frameworks?

Absolutely. Most API testing tools offer integrations with popular programming languages such as Java, JavaScript, and Python. This makes it easier for development teams to build, run, and maintain tests directly within their existing tech stacks. Whether you’re testing a Java application or another platform, language support enhances adoption and flexibility.

How We Can Help You

With over 16 years of experience and a global presence, Abstracta is a leading technology solutions company with offices in the United States, Chile, Colombia, and Uruguay. We specialize in software development, AI-driven innovations & copilots, and end-to-end software testing services.

Our expertise in API tests combined with our comprehensive testing strategy spans across industries, enabling us to deliver tailor-made solutions that enhance both security and performance. By partnering with us, you gain access to the best tools and experts in API testing.

We believe that actively bonding ties propels us further and helps us enhance our clients’ software. That’s why we’ve built robust partnerships with industry leaders Microsoft, Datadog, Tricentis, Perforce BlazeMeter, and Saucelabs to provide the latest in cutting-edge technology. 

Our holistic approach enables us to support you across the entire software development lifecycle.

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