For any business, any industry, software applications are now almost indispensable. And, for those software applications to work seamlessly, implementation of Application Programming Interface (API) is inevitable.

With API being so significant, testing of these APIs is equally vital. As projected by Google Trends, the overall interest in API testing globally has been rising increasingly. For API testing to be done perfectly, choosing the apt process, tool and solution is a must.

There are many API testing tools available, from which organizations can choose the right one as per the need. But, before we go through the testing tools for API, let us quickly glance through what API and API testing is.

What is API?

API is a vital software intermediate that facilitates effective talking of two applications/systems to each other. It is an important element for all software applications since it acts as a mediator between two programs. It defines how the software should interact with another software.

Key Benefits of API

• Offers effective client experience
• Enhances productivity and efficiency
• Garners data for BI and analytics
• Increases seamless connection and collaboration
• Builds up better business opportunities
• Saves bigtime on costs

What is API Testing?

API testing aims to find out if the API involved in the projects is competent to fulfill the requirements related to the application’s functionalities, reliability, performance, and security. Once the logic is worked upon, relevant tests can be developed to find out the correctness of the data.

API testing helps in finding out errors, inconsistencies, and differences from what is expected. It includes testing of the API components individually and as a part of the integration testing between software components.

Amongst the three main layers in any app – the presentation layer, business layer, and database layer; API testing is done in the middle business layer between the database layer and presentation layer. Here, the entire business logic administering is done with all transactions interacting between the two layers.

It facilitates communication between software units along with proper data exchange. It also confirms the logic of the constructed architecture.

The different API testing types include validation testing, functional testing, UI testing, security testing, fuzz testing, load testing, penetration testing, runtime, and error detection.

Key Benefits of API Testing

• Extracting bugs and issues at an early stage
• Enhanced test coverage
• Lesser testing costs
• Language and GUI independent
• Effective time usage with faster releases

15 Best API Testing Tools to Look For in 2022

• Paw
• RapidAPI
• Postman
• SoapUI
• Katalon Studio
• JMeter
• REST-assured
• Karate DSL
• Parasoft SOAtest
• Eggplant
• Tricentis
• vREST
• Ping API
• Airborne
• Apigee

Paw

Considered an advanced API testing tool for Mac, Paw is a completely featured HTTP client that undergoes testing of APIs that are created or used. It has an effective native macOS interface for creating HTTP requests, inspecting server responses, and generating client code. It natively supports JSON schema and offers compliance with Swagger and RAML descriptions.

Key Features

• Easy to use and effective user interface
• Highly stable in terms of performance
• Multi-dimensional environment settings
• Intuitive feature building
• Real-time synchronization
• Full-featured visual HTTP client
• Provides team products
• Free trial accessible
• Wide documentation and extensions
• Easy request organization
• JSON outline editor and viewer
• Support for third-party tools like Amazon S3, OAuth 1 & 2 etc.

RapidAPI

RapidAPI is the next-gen API testing tool that has over a million developers who leverage it for testing and connecting to thousands of APIs. Through internal and external APIs, developers can collaborate on APIs with this tool. There are RapidAPI Teams and RapidAPI Hub that helps in the testing of internal APIs. By using a single SDK, API key and a dashboard, RapidAPI can offer a collaborative experience right from development to testing and monitoring.

Key Features

• Thousands of APIs to support
• Supports multiple API types
• Offers good documentation and code snippets
• Free for use and comprehensive testing
• Flexible testing of APIs as many as needed
• Easy searching and testing of APIs
• Single workspace for 10000 public APIs
• Global monitoring
• Seamless native integration to other RapidAPI products
• Free for use up to 100000 API calls
• Unlimited testing
• Fast creation of comprehensive tests
• CI/CD integration to GitLab, GitHub etc.
• Provision of real-time alerts through email, SMS etc.
• All in one testing product
• Continuous test runs for better API monitoring

Postman

Postman is yet another popular API testing tool that provides a desktop and web version for testing API services. It empowers the teams to have a collaborative sharing of knowledge. It is easy to use and has the competence to store commands. It is easy for developers to set up parameters on method calls. It has a strong HTTP client for testing of web services and almost all modernized web API data can be obtained. It is considered trustworthy to transmit and receive REST information.

Key Features

• Creating, sending, and saving of requests (REST, SOAP, GraphQL)
• Editing request headers
• Managing cookies linked with different domains
• Ease of use, user friendly and accessible
• Request tracking competencies
• Uses a graphical user interface
• Easily setting up parameters
• Competence to store commands and provide API development
• Extraction of modernized web API data
• Boolean test writing
• Creation of REST call collection
• Hassle-free and rich interface
• Easily transmit and receive REST information
• Utilized for exploratory and automated testing
• Can execute with ease on Mac, Linux, Windows, Chrome apps
• No need to learn a newer language
• Third-party integration features for Swagger, RAML, etc.
• Easy sharing of knowledge within the teams

SoapUI

SoapUI is a popular functional testing tool for web service and SOAP testing. It helps developers to easily test SOAP, REST, GraphQL and web services. It offers the teams an effective solution for creating and executing complicated tests on web services. Custom codes can also be created using Groovy. There are different elements like test reports, SOAP API testing etc. that can be of great help to developers. It offers seamless integration with many API management platforms.

Key Features

• Easily usable graphical user interface
• Enterprise-ready features
• Open-source with effective work storage
• Data transfer without manual intervention
• Fast creation of tests with drag and drop features
• Data-driven testing
• Creates custom code using Groovy
• Easy to store work with a provision to access it anytime
• Reusable scripts, tests, and security scans
• Seamless integration with API management platforms
• Complete access to full source code
• Auto mock creation
• Code-free and asynchronous testing environment
• Simplifies complicated tasks
• Supports REST, SOAP, JMS, JDBC etc.
• CI/CD integration
• Support for extended HTTP like COPY, UNLOCK, PURGE etc.

Katalon Studio

Developed by Katalon, Katalon Studio is a free and automated API testing tool that is created on top of frameworks like Selenium, Appium. It has a special IDE interface for mobile, web, API, and desktop app testing. It offers simple development with all popular frameworks and plug-ins consolidated at a single location. It is apt for novices and experienced developers. It supports SOAP and RESTful requests with effectiveness.

Key Features

• Good support for CI/CD integration
• Usable for automated and exploratory testing
• Comprehensive package and framework for API, Desktop, Mobile testing, etc.
• Seamless importing of tests from external frameworks
• Better test coverage and accuracy
• Offers insightful reports and dashboards for better collaboration
• Support for SOAP and RESTful requests, data-driven approach
• Support for exploratory and automated testing
• Ideal for novices and experts via Groovy and Manual Scripting modes
• Integrates well with Katalon TestOps, UI, and API/web services across platforms
• Supports AssertJ for creation of assertion with BDD style
• Intuitive IDE
• Easily maintainable API tests
• Supports parameterized and command functions
• Encourages data-driven approach

JMeter

Powered by Apache, JMeter is an open-source API testing tool that is a cent percent Java application. It is used extensively as a load testing tool to analyze and measure the performance of multiple web services. It is mainly used for functional API testing and helps in enhancing the performance of testing. It offers good support for repeating test results and per-thread cookies. The user interface is quite user-friendly and can be utilized as a command-line interface.

Key Features

• Works automatically with CSV files
• Used for static and dynamic resources performance testing
• Simulates high load on the server
• Analyses complete performance under various load types
• Highly extensible core
• Multi-threading framework
• Data analysis and visualization
• Encourages developers for replaying test results
• Supports per-thread cookies
• Flexible and customizable
• Helps teams create unique parameter values for testing
• Includes API tests in the CI pipelines through Jenkins
• Can use various programming languages
• Performance and load testing of different servers and protocols
• Quick data creation through CSV files

REST-assured

Considered one of the apt API testing tools in Java, REST-assured possesses an open-sourced platform that has a Java Domain-specific language. It is used for simplified testing of RESTful web services. It can be utilized for REST web services, coordinating response content for testing. Developers don’t need to be good at HTTP, for testing web APIs through this tool. Also, it eliminates the need of writing lots of code to set up an HTTP connection, send a request, and get a response.

Key Features

• No need to be an HTTP expert
• Inbuilt functions, saves time on coding
• Behaviour Driven Development
• Support of XML Path and JSON Path syntax
• Human readable and understandable tests
• Creation of customizable HTTP requests
• Testing REST services in Java
• Supports syntax of BDD testing
• No need to code from the start
• Seamless integration with Serenity integration framework
• Authentication methods for API validation
• Supports various HTTP methods and other methods too
• Creation of effective and beautiful reports
• Integrates well with CI/CD tools

Karate DSL

Karate DSL is a popular framework for API automation testing, load testing, and performance testing. It is based on the Cucumber library and assists in creating scenarios for API-based tests simplistically. It runs on Java and uses Apache HTTP client for performing connections. There is a well connected with the Gatling framework and with the help of a domain-specific language, testers can come up with meaningful tests.

Key Features

• Permits configuration switching
• Good support for multi-thread parallel execution
• Supports XML and JSON
• Easy to understand syntax even for novices
• Collective API Automation and performance testing into a single standalone tool
• Integration with popular Java unit testing frameworks
• A good option for testing GraphQL
• Multi-threaded parallel execution
• Testing and generation of reports
• Reuse of payload data and user-defined functions
• Java knowledge is not compulsory
• Powerful assertion competencies
• Perfect for testing BDD

Parasoft SOAtest

Parasoft SOAtest is a well-known API testing tool that is anchored in AI and ML. It offers simplification of complicated functional testing across databases, APIs, UIs, etc. There is regular monitoring of quality for Agile and DevOps teams. It creates a codeless API test scenario from the manual recording that is reusable, robust, and shareable. There is an effective transformation of your test objects into security tests, reusable components, and lesser redundancy.

Key Features

• Simplifies test maintenance
• Garner rapid feedback from CI/CD pipeline
• Easy implementation of codeless testing
• Delivers different testing types like API, Microservices, Web UI, API security etc.
• End to end testing

Eggplant

Eggplant, as a leading test automation solution is a good API testing tool that adheres to your needs to fasten deployments and reduce testing efforts. It offers comprehensive testing for your APIs. It is majorly utilized for rich internet application testing, mobile testing, performance testing, and cross-platform testing. It finds out the inconsistent behavior in the APIs much before users confront them.

Key Features

• Makes use of intelligent image recognition algorithms
• Combination of API testing with UI validation to get a real-world effect
• Pre-configured snippets, parameters for easy execution of API tests
• Easy appending of steps beyond API calls
• Auto-generation of test automation elements
• Early recognition of abnormalities prior to user encounter

Tricentis

Tricentis is a popular software testing tool that is effective for the automation of comprehensive testing of software applications. It is a robust tool that supports multiple protocols like RabbitMQ, SOAP, REST, etc. It has effective integration into the Agile and DevOps cycle. It leverages the model-based test automation making script maintenance easy. The testing can span across mobile, cross-browser, packaged apps, etc.

Key Features

• Optimization and acceleration of testing
• AI-powered and codeless approach
• Removes blockages out of testing
• Makes use of cloud services for easy access in the Cloud
• High scalability and reusability
• Lessens the time of regression testing
• Dashboards and effective reports
• Usability across devices
• Model-based test automation
• Supports a variety of protocols like HTTP, JMS, Rabbit MQ, SOAP, REST, etc.
• Comprehensive API testing

vREST

vREST is an effective API testing tool that offers an online solution for automated testing. It offers a complete solution for fast validation of your REST APIs, delivering a defect-free web app and automatic recoding of REST/RESTful APIs. For understanding this tool and testing with it, not many of skills are needed. It is easy to learn and there is detailed documentation available for API-related specifications.

Key Features

• Creation of API mocks with Mock Server
• Regression testing of applications
• Recording and replaying of test cases
• Powerful response validation
• Lessening dependency amongst teams
• Easy integration with third-party tools
• Automatic test, mock, record, and specification of API
• Mock server functionality

Ping API

Ping API is a known testing tool that powers the writing of test scripts in JavaScript for API testing. It helps inspection of an HTTP API call with a complete request. Users get notifications via email or chat.  It is a cloud-based service in which an AI layer is added as a security layer through the API gateways. This results in an increase of the security of your API structure. Here is support available for scriptwriting for validation of response header and body.

Key Features

• Automatic API discovery
• Scheduling of API every hour or minute
• AI availability for all API
• Enriched traffic visibility and reporting
• Boosts customer engagement
• Real-time intelligence for API-based security
• Support for script writing
• Validation of CRUD (Create, Read, Update, Delete) flow
• Set requests for header, body, URL
• Inspects HTTP API call with full-on request and response data

Airborne

Airborne is a popular API automation tool that is leveraged by REST API testers for effective testing. It is an RSpec-driven API testing framework that writes automatic tests for APIs. It is Ruby equivalent and offers a simple response check with the relevant types of data. It utilizes the RestClient to manage the HTTP requests with accuracy and maturity. Writing simple tests is easier for developers and testers.

Key Features

• Testing of APIs on top of RestClient and Rspec
• Ruby equivalent
• Programming and REST API testing framework
• Works on APIs written with Ruby on Rails
• Works well with Rack applications
• Easy to remember few main methods
• Trustworthy and robust
• Limited UI exposure required to write code
• No UI is needed apart from the text file for code creation

Apigee

Apigee is a part of Google Cloud and a cross-cloud API testing tool. It helps testers test different parameters based on the API performance. It takes help from editors just as Swagger etc. it is good for designing, monitoring, deploying, and scaling APIs. With ease, it can create API proxies from Open API specifications and can easily go in for cloud-based deployment.

Key Features

• Availability of governance and security policies across all APIs
• Identification of performance problems
• Easy tracking of API traffic, response times, and error rates
• Fronting services with a proxy layer
• Offers security, quotas, analytics, and rate-limiting
• Tracks API traffic, response time, and error rates
• Support for Node.js
• Direct control and powered by JavaScript
• Easy creation of API proxies
• Multi-step, powered by JavaScript
• Cloud, on-premises, or hybrid model on a single code base
• Meant especially for digital business

As We Wrap Up

APIs are the fundamental component of any software application and hence API testing tools are highly important for the success of any project. The above list is an extensive one that showcases all key, popular API testing tools. Choosing the ideal one depends upon many parameters like resources, budget, project needs, skill set available, and more. Finally, to each its own!