Top 10 API Testing Tools in 2023

Developers use a combination of APIs to make the majority of web and cloud services accessible. However, before the services become accessible to consumers, they must undergo a process. This procedure, known as API testing, verifies the API’s optimal performance.

API testing is not easy, but API testing tools significantly simplify the process. These tools are essential for ensuring the quality of the APIs and backend applications’ code.

What is API Testing?

API testing is a procedure used by developers to evaluate the functionality, efficacy, and security of APIs. Before releasing their software, the results of this procedure will inform developers if an API requires problem fixes and patches.

They accomplish this through a simulation that entails sending queries or traffic that would reach the API when it is accessible to its users, regardless of whether it is authentic or not. They observe the API to determine how it will react to this volume of traffic. If the results are positive, integrating the API is secure. If not, they will be required to fix it, contingent on the API’s complexity, or forfeit the entire prize.

What are the three types of API Testing?

API testing can be broadly categorized into three main types:

1. Unit Testing (Component Testing): Unit testing is the lowest level of API testing, focusing on individual units or components of the code, typically at the function level. The purpose of unit testing is to verify the correctness of specific functionalities or methods within an API in isolation.
2. Integration Testing: Integration testing involves testing the interactions and integration points between different components, modules, or systems within an API. The primary goal is to ensure that the integrated components work cohesively and as expected when combined together.
3. End-to-End Testing (Functional Testing): End-to-end testing evaluates the entire API system, including all components, databases, external services, and communication interfaces.The focus is on testing the complete flow of data and operations from the client to the server and back, simulating real-world scenarios.

What is an API Tool?

An API tool is a software application or platform designed to facilitate the development, testing, monitoring, and management of Application Programming Interfaces (APIs). APIs are sets of rules and protocols that allow different software applications to communicate and interact with each other. API tools play a crucial role in the software development process by providing various functionalities to simplify and enhance API-related tasks, especially API Testing.

What to look for in an API Testing Tool?

As API testing has become an essential step in the software development life cycle, the global markets have witnessed a surge in API tools. While many API tools can adequately assess APIs, only a handful can effectively evaluate all API layers.

Developers often struggle to find the right tools that align with the complexity of their API testing requirements. Nevertheless, certain indicators can help in selecting the most suitable API testing tool:

1. Seamless integration with continuous integration and deployment pipelines.
2. Capability to perform concurrent random tests.
3. User-friendly interface for easy navigation.
4. Swift response time during operations.
5. Availability of comprehensive API documentation.

9 Top API Testing Tools in 2023

The Top 9 API Testing Tools in 2023 are:

1. SOAPUI
2. Test Studio
3. Postman
4. OWASP ZAP
5. Rest Assured
6. Apache JMeter
7. Rapid API
8. Karate DSL
9. Google Apigee API

1. SOAPUI

SoapUI is a specialised tool designed for testing REST, SOAP, and GraphQL APIs. It offers a comprehensive API testing solution with a strong emphasis on convenience for developers and testers through its user-friendly graphical interface.

The tool enables the execution of automated functional, regression, and load tests, making it suitable for various testing scenarios.

Advantages of SOAPUI

SoapUI offers several key benefits that make it a preferred choice for API testing:

• Thorough API Testing: SoapUI provides a wide range of tools and features that enable comprehensive API testing. It supports testing for REST, SOAP, and GraphQL APIs, allowing testers to evaluate various types of APIs in one platform.
• Open-Source Code Methodology: Being based on an open-source code methodology, SoapUI allows users to access and modify its source code. This offers greater flexibility and customization options to tailor the tool according to specific testing requirements.
• One-Stop Solution: SoapUI’s versatility and various functionalities make it a complete and all-inclusive solution for API testing. Whether it’s functional, regression, or load testing, the tool covers all essential aspects of API evaluation, eliminating the need for multiple testing tools.

Limitations of SOAPUI

SoapUI, like any software tool, has its disadvantages. Some of the drawbacks of SoapUI include:

• Lower Stability: Some users have reported that SoapUI may have occasional stability issues, leading to crashes or unexpected behavior during testing. While the tool is generally reliable, these instances of instability can be frustrating for users.
• Steep Learning Curve: SoapUI’s interface and features can be overwhelming for first-time users, especially those new to API testing. Navigating through the tool and understanding its capabilities may require some initial effort and training.
• Dependency on WSDL for Web Service Testing: SoapUI heavily relies on Web Services Description Language (WSDL) files for testing web services. While WSDL is a standard way to describe web services, some APIs might not have well-defined or readily available WSDL files, which can hinder testing in such cases. 

2. Test Studio

Test Studio by Progress Telerik provides a user-friendly and easy-to-maintain testing solution for users. It offers seamless integration of RESTful APIs into various environments, enabling efficient API testing. 

With Test Studio, users can automate API testing without the need for coding, ensuring thorough validation of the model’s integrity and reliability.

In summary, Test Studio streamlines the API testing process by offering a simple and code-free approach, making it accessible to a broader range of users while ensuring the accuracy and dependability of the tested APIs.

Advantages of Test Studio

Test Studio offers several advantages that make it a compelling choice for API testing and other testing needs:

• User-Friendly Interface: Test Studio provides a user-friendly and intuitive interface, making it easy for both technical and non-technical users to create and manage test cases effectively. Its visually-driven testing approach reduces the learning curve and enhances productivity.
• Codeless Automation: One of the standout features of Test Studio is its codeless automation capabilities. Users can automate test scenarios without writing extensive code, which accelerates the testing process and allows testers with limited coding knowledge to contribute effectively.
• End-to-End Testing: Test Studio supports end-to-end testing, covering various aspects of the application, including APIs, web, desktop, and mobile. This all-in-one testing solution simplifies the testing process and provides a comprehensive assessment of the application’s functionality and performance.

Limitations of Test Studio

While Test Studio offers numerous advantages, it also has some potential disadvantages that users should consider:

• Cost: Test Studio is a commercial testing tool, and its licensing cost may be a significant factor for small teams or individual testers with limited budgets. The pricing structure may not be feasible for all organizations, especially those looking for free or open-source alternatives.
• Learning Curve: Despite its user-friendly interface, Test Studio may still have a learning curve, especially for users who are new to automated testing tools or those with limited technical background. Training and getting accustomed to the tool’s features may take some time.
• Limited Platform Support: Test Studio may have limitations in terms of supporting certain platforms or technologies, which could be a concern for organizations working with specific environments or frameworks that are not fully compatible with the tool.

3. Postman

Postman is a leading API testing tool that is compatible with Linux, MacOS, and Windows operating systems. It offers a wide range of features, allowing users to create functional, integration, and regression tests efficiently.

Users can choose between using the Command Line Interface (CLI) or a Graphical User Interface (GUI) that is easy to navigate.

Key Features of Postman

• User-Friendly Interface: Postman provides an interface that caters to users of all levels. Experienced testers can leverage its scripting capabilities, while beginners can achieve good results without much complexity using the GUI.
• Automated Testing: Postman supports automated testing, enabling users to monitor APIs and execute various requests for testing and debugging purposes. This automation streamlines the testing process and improves efficiency.
• Runtime Support for Popular Patterns and Libraries: Postman’s runtime supports widely used patterns and libraries, facilitating quick testing and debugging of APIs with familiar tools.

Advantages of Postman

• User-Friendly Interface: Postman’s intuitive and user-friendly interface makes it accessible to users of all levels, including beginners and experienced testers.
• Cross-Platform Compatibility: Postman is compatible with Linux, MacOS, and Windows, allowing users to access and utilize the tool on different operating systems.
• Versatile Testing Capabilities: Postman supports various testing types, including functional, integration, and regression testing, enabling comprehensive API evaluation.

Limitations

• Dependency on Cloud Features: Some advanced features in Postman, such as API monitoring, require a cloud subscription, which may involve additional costs for organizations.
• Limited Offline Capabilities: While Postman offers some offline functionality, certain features may require an internet connection, which can be restrictive in certain testing environments.
• Learning Curve for Advanced Features: Although Postman’s basic functionalities are easy to grasp, leveraging more advanced features and scripting may have a steeper learning curve for less experienced users.

4. OWASP ZAP

OWASP ZAP (Zed Attack Proxy) is a widely used open-source security testing tool designed to help identify and prevent security vulnerabilities in web applications. 

It is one of the projects maintained by the Open Web Application Security Project (OWASP), an organization focused on improving the security of software.

Key Features of OWASP ZAP:

• Web Application Security Testing: OWASP ZAP is primarily used for security testing of web applications. It can assess and identify common security vulnerabilities like cross-site scripting (XSS), SQL injection, cross-site request forgery (CSRF), and more.
• Intercepting Proxy: OWASP ZAP acts as an intercepting proxy, allowing testers to monitor and modify requests and responses between the client and the web server. This enables users to inspect and manipulate the application’s traffic for security testing purposes.
• Automated Scanning: The tool offers automated scanning capabilities to identify security vulnerabilities in web applications quickly. Users can run predefined security scanning policies or create custom scanning configurations.

Advantages of OWASP ZAP

OWASP ZAP (Zed Attack Proxy) offers several advantages that make it a popular choice for web application security testing:

• Comprehensive Security Testing: OWASP ZAP provides a wide range of security testing capabilities, allowing users to identify common security vulnerabilities in web applications, including cross-site scripting (XSS), SQL injection, CSRF, and more
• Open Source and Free: Being an open-source tool, OWASP ZAP is freely available to everyone, making it accessible to organizations of all sizes and budgets.
• Active and Passive Scanning: OWASP ZAP supports both active and passive scanning, enabling users to perform automated security tests and observe application traffic for potential vulnerabilities.

Overall, OWASP ZAP’s robust security testing capabilities, open-source nature, automation support, and strong community backing make it a valuable asset for organizations looking to enhance the security of their web applications and prevent potential cyber threats.

Limitations of OWASP ZAP

While OWASP ZAP is a powerful and widely-used security testing tool, it also has some limitations that users should be aware of:

• False Positives/Negatives: Like any security testing tool, OWASP ZAP may generate false positives (identifying vulnerabilities that do not exist) or false negatives (failing to detect certain vulnerabilities). Manual verification is often required to confirm the validity of reported issues.
• Learning Curve: OWASP ZAP has a learning curve, especially for users who are new to security testing or not familiar with web application security concepts. Becoming proficient in utilizing all the tool’s features may require time and practice.
• Resource Intensive: Running comprehensive security scans with OWASP ZAP can be resource-intensive, especially for large and complex web applications. Scanning may lead to increased memory and CPU usage, affecting the overall performance of the testing environment.

5. REST Assured

REST Assured is a popular testing framework for RESTful APIs that caters to developers familiar with the Java programming language. 

It simplifies API testing by providing a convenient syntax, allowing testers to create requests without the need to write code from scratch.

Key Features of REST Assured:

• No Need to Understand HTTP: Users of REST Assured do not require an in-depth understanding of the HTTP protocol, as the framework abstracts the complexity and provides a user-friendly interface for API testing.
• Java Compatibility: REST Assured is designed for Java developers and can be easily integrated into Java projects. Users need Java version 8.0 or higher to utilize the tool effectively.
• Integration Testing: REST Assured supports integration testing, enabling users to test API endpoints and interactions with other components or systems in a holistic manner.

Advantages of REST Assured

REST Assured offers several advantages that make it a popular choice for API testing, particularly for developers familiar with Java:

• Simplified API Testing: REST Assured provides a user-friendly and straightforward syntax, making it easy for developers to write API tests without the need to deal with complex HTTP details. This simplicity enhances the efficiency of API testing.
• Integration with Java Projects: Being a Java-based framework, REST Assured seamlessly integrates with Java projects, enabling developers to incorporate API tests directly into their existing codebase.
• Readable Test Code: REST Assured’s expressive syntax allows developers to write API test code in a clear and readable manner. This readability makes it easier to understand test scenarios, promoting better collaboration among team members.

Limitations of REST Assured

While REST Assured is a powerful and popular tool for API testing, it also has some limitations that users should be aware of:

• Java Dependency: REST Assured is designed for Java developers, which means users without Java programming skills may find it challenging to use or understand the framework.
• Learning Curve: For testers who are new to REST Assured or API testing in general, there may be a learning curve, particularly if they are not already proficient in Java.
• Limited Language Support: REST Assured primarily focuses on Java, which means teams with developers proficient in other programming languages may not be able to fully utilize the tool’s capabilities.

6. Apache JMeter

Apache JMeter is a powerful testing tool primarily intended for users with Java experience. It excels in conducting functional and performance tests for REST, SOAP services, and other APIs. 

With JMeter, users can simulate high request loads on their APIs to assess their performance under various scenarios.

Key Features of Apache JMeter:

• Load and Performance Testing: JMeter is well-known for its ability to conduct load and performance tests on APIs, enabling users to evaluate how their services perform under different levels of stress and traffic.
• Compatibility: JMeter is compatible with various operating systems, including macOS, Linux, and Windows, providing flexibility for users to run tests on their preferred platforms.
• CLI and GUI Options: JMeter offers both a Command Line Interface (CLI) and a Graphical User Interface (GUI), making it accessible to users who prefer a command-line environment or a user-friendly GUI for test creation and execution.

Advantages of Apache JMeter

Apache JMeter offers several advantages that make it a preferred choice for load and performance testing, particularly for API testing:

• Load and Performance Testing: JMeter is specialized in load and performance testing, enabling users to simulate high traffic loads on APIs to assess their performance, scalability, and reliability under various conditions.
• Versatility: JMeter is not limited to API testing alone; it can be used to test a wide range of applications and protocols, including web applications, databases, FTP, and more, making it a versatile testing tool.
• Open Source and Free: JMeter is an open-source tool, which means it is freely available to users without any licensing costs. This makes it accessible to organizations of all sizes and budgets.

Limitations of Apache JMeter

While Apache JMeter is a powerful and widely-used tool for load and performance testing, it also has some limitations that users should be aware of:

• Steeper Learning Curve: JMeter’s extensive functionality and versatility may lead to a steeper learning curve, especially for users new to performance testing or load testing concepts.
• Resource Intensive: When conducting large-scale load tests, JMeter can consume significant system resources, including memory and CPU, which may impact the performance of the testing environment.
• Limited GUI Performance with Large Test Plans: JMeter’s GUI can become sluggish and unresponsive when handling large and complex test plans, potentially affecting the user experience during test creation and modification.

7. Rapid API

Rapid API is a versatile API testing and monitoring tool that supports deep functional testing for REST, SOAP, and GraphQL APIs. 

It emphasizes improved efficiency by enabling seamless integration into CI/CD pipelines and promoting easy collaboration among teams through RapidAPI and RapidAPI Enterprise hub.

Key Features of Rapid API:

• Comprehensive Testing Environment: Rapid API provides a comprehensive testing environment, catering to both beginners and experts. Users can create and conduct API calls and tests in a user-friendly interface.
• Support for Various API Types: The tool supports testing for a wide range of API types, including REST, SOAP, and GraphQL, making it suitable for testing diverse API architectures.
• Global Monitoring: Rapid API offers a global monitoring feature that assesses API tests through reports, analytics, and other monitoring capabilities, allowing users to track the performance and health of their APIs across different locations.

Advantages of Rapid API

Rapid API offers several advantages that make it a valuable tool for API testing and monitoring:

• Comprehensive Testing Support: Rapid API supports deep functional testing for various types of APIs, including REST, SOAP, and GraphQL. This versatility allows users to test and monitor APIs with different architectures and protocols.
• User-Friendly Interface: The tool provides a friendly and intuitive interface, accommodating both beginners and experienced testers. This ease of use makes it accessible to a wide range of users without requiring extensive technical expertise.
• Effortless Integration with CI/CD Pipelines: Rapid API’s seamless integration with continuous integration and continuous delivery (CI/CD) pipelines streamlines the testing process, enabling automated testing as part of the development workflow. This improves efficiency and ensures consistent testing practices.

Limitations of Rapid API

While Rapid API offers various advantages, it also has some limitations that users should consider:

• Limited Protocol Support: While Rapid API supports testing for popular API protocols like REST, SOAP, and GraphQL, it may have limited support for less common or niche protocols, potentially limiting its usage for specific API types.
• Platform Dependency: Rapid API may be designed and optimized for specific platforms, which could lead to limited compatibility with certain operating systems or environments.
• Learning Curve: Users who are new to Rapid API or API testing tools, in general, may face a learning curve when getting started with the tool, especially if they are not familiar with API testing concepts.

8. Karate DSL

Karate is a versatile testing tool that offers various services for testers to create simulations and assess API performance. Its predefined steps make it user-friendly for beginners and time-saving for developers who seek rapid testing experiences.

Key Features of Karate:

• Karate DSL: Karate is based on the Cucumber-JVM framework and offers a domain-specific language (DSL) that simplifies API test automation, UI automation, and performance testing, all within the same environment.
• Unified Environment: With Karate, testers can perform API test automation, UI automation, and performance testing in a single integrated environment, eliminating the need for separate tools for different testing aspects.
• Debugging and Issue Fixing: Karate’s debugging feature allows testers to replay steps during the assessment, making it seamless to identify and fix issues in APIs, enhancing the overall testing efficiency.

Advantages of Karate DSL

Karate DSL offers several advantages that make it a popular and powerful testing tool for API test automation and more:

• Unified Testing Environment: One of the major advantages of Karate DSL is its ability to support API test automation, UI automation, and performance testing in a single integrated environment. This eliminates the need for multiple tools and streamlines the testing process.
• Cucumber-JVM Integration: Karate DSL is based on the Cucumber-JVM framework, which provides a behavior-driven development (BDD) approach. This allows for easy collaboration between testers, developers, and other stakeholders through the use of plain English Gherkin syntax.
• User-Friendly Predefined Steps: Karate DSL comes with a set of predefined steps, making it easy for both beginners and experienced testers to create test scenarios without having to write complex code from scratch. This saves time and effort and helps accelerate the testing process.

Limitations of Karate DSL

While Karate DSL offers numerous advantages, it also has some limitations that users should be aware of:

• Limited Learning Resources: Compared to some other testing tools, Karate DSL may have fewer learning resources, documentation, and tutorials available, which could make it slightly challenging for beginners to get started.
• Smaller Community Size: While Karate DSL has an active community, it may be smaller compared to some other popular testing tools. This could mean fewer readily available plugins, integrations, and community support compared to more widely adopted tools.
• Limited Protocol Support: While Karate DSL is highly capable for API test automation, UI automation, and performance testing, it may have limited support for less common or niche protocols, potentially limiting its applicability to specific use cases.

9. Google Apigee

Apigee API is a powerful and reliable tool that provides a comprehensive set of features for designing, monitoring, testing, and securing APIs. 

Built with multi-step JavaScript capabilities, it offers users the flexibility to manage their API features efficiently. Apigee API allows tracking and analyzing API traffic, response behavior, and error rates, ensuring optimal performance and reliability.

Key Features of Apigee API:

• API Design and Management: Apigee API facilitates the design and management of APIs, allowing users to define endpoints, request/response formats, and policies for API behavior.
• API Monitoring: The tool offers robust monitoring capabilities, enabling users to track API traffic, usage patterns, performance metrics, and error rates. This helps in identifying and resolving potential issues proactively.
• API Testing: Apigee API supports API testing, allowing users to verify the functionality and correctness of their APIs through various test scenarios.

Advantages of Apigee API

Apigee API offers several advantages that make it a leading API management platform in the industry:

• Comprehensive API Management: Apigee API provides a complete set of tools and features for designing, monitoring, testing, and securing APIs. It offers a unified platform for end-to-end API management, simplifying the entire API lifecycle.
• Scalability and Performance: Apigee API is designed to handle high traffic volumes and large-scale API deployments. Its architecture ensures scalability and maximum performance, making it suitable for enterprise-level applications.
• Flexibility with JavaScript Policies: The multi-step JavaScript policy framework in Apigee API allows users to implement custom logic and workflows in their APIs, providing the flexibility to meet specific business requirements.

Limitations of Apigee API

While Apigee API offers many advantages, it also has some limitations that users should consider:

• Cost: Apigee API is a feature-rich API management platform, but it can be relatively expensive, especially for small businesses or projects with limited budgets. Organizations need to carefully evaluate the cost versus benefits for their specific use case.
• Learning Curve: Implementing and managing Apigee API may have a learning curve, especially for teams and developers who are new to the platform and API management concepts. Training and onboarding may be required for effective usage.
• Overhead for Small Projects: For small-scale projects or APIs with limited complexity, the extensive features of Apigee API may introduce unnecessary overhead, making it more suitable for larger and more complex projects.

Conclusion

API testing plays a crucial role in the software development process, and it offers several advantages over end-to-end testing. 

However, it’s essential to acknowledge some of the challenges and complexities associated with API testing tools:

1. Configuration and Setup: Setting up an API testing environment can be challenging, especially when dealing with complex APIs or integrating with external systems. 
2. Technical Knowledge Requirement: API testing often requires a good understanding of APIs, HTTP protocols, data formats like JSON and XML, and programming languages. 
3. Reporting: Some API testing tools might lack comprehensive reporting capabilities, making it challenging to analyse test results effectively. 

Browserstack Automate API enables users to retrieve information related to their Automate plan, project, build, and session details. These APIs follow the RESTful architectural style and utilise standard HTTP response codes for easy integration with other systems and tools.

Key features of BrowserStack’s Automate APIs:

• Access Test Information: With the REST API, users can access detailed information about their tests, including test plans, projects, builds, and specific session details.
• Command-Line Interface (CLI) Support: The API can be accessed through the command-line interface, allowing users to interact with the API directly from their terminal or command prompt.
• RESTful Architecture: The APIs are organised following REST principles, making them intuitive and easy to use. They use standard HTTP methods like GET, POST, PUT, and DELETE for performing various operations.

Overall, BrowserStack’s Automate APIs provides teams with the ability to access and manipulate test-related data programmatically. This enables greater flexibility, automation, and integration with other tools and systems, making it a valuable feature for teams seeking to streamline their testing workflows and improve their testing processes.

Try BrowserStack for Free