Best API Testing Tools for 2020 (Updated list) | Software Testing Material

API testing (Application Programming Interface Testing) is a software testing type that focuses on the determination if the developed APIs meet expectations regarding the functionality, reliability, performance, and security of the application.

The interest in API testing has been growing steadily over the last couple of years, according to Google Trends. Research by Smartbear over 5,000 software professionals in 2017 showed the number of API testers automating more than 50% of their tests expected the numbers to grow by 30% ( from 59% to 77%) in the next two years and 80% of the survey participants reported they were responsible for testing APIs.

Having the right process, tool, and solution for API automation tests are more critical than ever. And with the shift-left trend, API testing is more than just a quality control solution but a crucial component of a success CI/CD deployment.

API Testing Tools

Top 10 API Testing Tools for 2020 (Details & Updates Done for You!)

This article will provide a summary of the top 10 API testing tools cover both open-source and commercial solutions that testing teams can select to suit their needs.

Comparison Table API Testing Tools

Top 10 API Testing Tools for 2020

1. Katalon Studio

Katalon Studio is a free automation test tool providing a common environment to create and execute UI functional, API/Web services, and mobile testing.

The capability to combine UI and Business levels (API/Web services) for different environments (Windows, Mac OS, Linux) has been considered an advantage of Katalon Studio.

Katalon Studio supports SOAP and RESTful requests with various types of commands (GET, POST, PUT, DELETE) with parameterized capability.

– Highlights:

  • Support combination test between UI and API verification.
  • Support testing both SOAP and RESTful requests.
  • Hundreds of built-in keywords for creating test cases.
  • Support one of the most powerful assertion library, AssertJ to create fluent assertion with BDD style.
  • Support the data-driven approach.
  • Can be used for both automated and exploratory testing.
  • Suitable for both pros and non-techies via the support of Manual and Groovy Scripting modes

Named as one of the 2020 Gartner Peer Insights Customers’ Choices for Software Test Automation — Katalon Studio has received more than 600 positive reviews, affirming its position at the forefront of the market.

Website: Katalon Studio

Pricing: Free – $69/license/month

2. Postman

Being originally a Chrome browser plugin, Postman now extends its solution with the native version for both Mac and Windows.

Complete Postman Tutorial

Postman is a good choice for API testing for those who don’t want to deal with coding in an integrated development environment using the same language as the developers.

  • Easy-to-use REST client
  • Rich interface which makes it easy to use
  • Can be used for both automated and exploratory testing
  • Can be run on Mac, Windows, Linux & Chrome Apps
  • Has a bunch of integrations like support for Swagger & RAML formats
  • Has Run, Test, Document and Monitoring Features
  • Doesn’t require learning a new language
  • Enable users to easily share the knowledge with the team as they can package up all the requests and expected responses, then send to their colleagues.

Website: Postman

Pricing: Free – $12/user/month

3. SoapUI

SoapUI is a headless functional testing tool dedicated to API testing, allowing users to test REST and SOAP APIs and Web Services easily.

Using SoapUI, users can get the full source and build the preferred features besides these abilities:

Free Package

  • Create test quickly and easily with Drag-and-drop, Point-and-click
  • Reusability of Scripts allows load tests and security scans to be reused for functional test cases in just several steps

Pro Package

  • Powerful data-driven testing: Data loaded from files, and databases, and Excel so that they can simulate how consumers interact with the APIs
  • Create complex-scenarios & support native CI/CD integrations, asynchronous testing

SOAPUI latest version 5.5 released in February 2019 had introduced the Endpoint Explorer dialog for users to send exploratory requests and analyze responses without creating a project. The tool also supports extended HTTP methods such as PROPFIND, LOCK, UNLOCK, COPY, PURGE.

Website: SoapUI

Pricing: Free – $659/year

4. Tricentis Tosca

Tricentis Tosca is a continuous testing platform for Agile and DevOps. Benefits of Tricentis Tosca include:

  • Supports many array of protocols: HTTP(s) JMS, AMQP, Rabbit MQ, TIBCO EMS, SOAP, REST, IBM MQ,NET TCP
  • Integrates into the Agile and DevOps Cycle
  • Maximize reuse and maintainability with model-based test automation
  • API tests can be used across mobile, cross-browser, packaged apps, etc…
  • Achieve sustainable automation with new technology
  • Reduce the time of regression testing
  • Interactive testing provides test managers with the ability to execute manual testing and collect results without having to configure Tosca environments.

The latest Tricentis Tosca version 13.1 released in March 2020 can support web service security configuration in the API Connection Manager. Users can use the signature security option to sign multiple parts of a message. In addition, from Tosca version 13.0, testers are allowed to read and write files dynamically with a file connection in the API Engine.

Website: Tricentis

Pricing: Contact Sales

5. Apigee

Apigee is a cross-cloud API testing tool, allowing users to measure and test API performance, supports, and build API using other editors like Swagger.

Additionally, Apigee is recognized as one of the leaders in the Gartner Magic Quadrant 2019 for Full Lifecycle API Management for the fourth consecutive time.

  • It is multi-step and powered by Javascript
  • Allows the design monitor, deploy, and scale APIs
  • Identify performance issues by tracking API traffic, error rates, and response times
  • Easily create API proxies from the Open API Specification and deploy them in the cloud
  • Cloud, on-premise, or hybrid deployment model on a single code base
  • PCI, HIPAA, SOC2, and PII for apps and APIs
  • Apigee is purpose-built for digital business, and the data-rich mobile-driven APIs and apps that power it.

Starting from February 2019 with the release of version 4.19.01, Apigee gave users even more flexibility to manage their APIs with features like Open API 3.0 support, TLS security, self-healing with apigee-monit, virtual host management improvements, and more software support. The latest announced in Apr 2020 with minor bug fixes only.

Website: Apigee

Pricing: Contact Sales

6. JMeter

JMeter (open source) is widely used for functional API testing although it is actually created for load testing.

  • Supports replaying of test results
  • Automatically work with CSV files, allowing the team to quickly create unique parameter values for the API tests.
  • Users can include the API tests in CI pipelines thank to the integration between JMeter and Jenkins
  • It can be used for both static as well as dynamic resources performance testing

The most recent release in November 2019 is JMeter 5.2. The tool has been packed with multiple features and enhancements, improved user experience, and many bug fixes, such as new protocol, JMESPath extractor, JDBC improvements, StringtoFile, HTTP Samplers.

Website: JMeter

Pricing: Open source

7. Rest-Assured

Rest-Assured is an open-source Java Domain-specific language that makes testing REST service more simple.

  • Have a bunch of baked-in functionalities, which means users don’t have to code things from scratch.
  • Integrates seamlessly with the Serenity automation framework, so that users can combine the UI and REST tests all in one framework that generates awesome reports.
  • Support BDD Given/When/Then syntax
  • Users don’t necessarily need to be an HTTP expert

Starting from version 4.0.0, Rest-Assured requires at least Java 8, instead of Java 6 as was previously required. This version also supported Apache Johnzon and fixed bunches of issues with the initial OSGi support. The latest version 4.2.0 announced in January 2020 allowed a nicer experience for Kotlin developers using the spring-mock-mvc module.

Website: Rest Assured

Pricing: Open Source

8. Assertible

Assertible is an API testing tool which concentrates on the automation and reliability.

  • Support for automating API tests through each step of a continuous integration and delivery pipeline.
  • Support for running API tests after deployments and integrates with familiar tools like GitHub, Slack, and Zapier.
  • Support validating HTTP responses with turn-key assertions such as JSON Schema validation and JSON Path data integrity checks
  • The Sync feature allows users to update tests when their specifications change, so they are no longer have to manually update their tests after adding new parameters or changing the response of API.

In October 2019, Assertible introduced the latest feature called Encrypted variables, which provides a new way to store tokens, passwords, and secret data fields required by tests to improve API testing security practices. Encrypted variables are not only trivial to use, but build on the cryptographically sound methodology for safe storage.

Website: Assertible

Pricing: Free – $100/month

9. Karate DSL

Karate DSL is a new API testing tool which help create scenarios for API-based BDD tests in a simple way without writing step definitions. Those definitions have been created by KarateDSL so that users can kickstart the API testing quickly.

  • Build on top of Cucumber-JVM
  • Can run a test and generate reports like any standard Java project
  • A test can be written without any Java knowledge required
  • Tests are easy to write even for non-programmers
  • Supports configuration switching/staging, multi-threaded parallel execution

Starting from the version 0.9.3, Karate UI is no longer part of the open-source tool’s core but a separate Maven artifact. This version included built-in support for WebSocket that is based on the async capability. The latest update Karate UI 0.9.5 in February 2020, came with web browser automation which allows users to submit a self-contained snippet of HTML as a full-fledged project — to demo or replicate issues.

Website: Karate

Pricing: Open Source

10. Swagger

Swagger is an API testing tool that allows users to start their functional, security, and performance testing right from the Open API Specifications. Swagger tooling and Ready API platform make it easy to quickly create, manage, and execute API tests in the pipeline.

  • Swagger Inspector provides capabilities to inspect API request-responses, and make sure they perform as expected
  • Import user’s API definitions to easily validate schema rules, automatically generate assertions against endpoints and inject synthetic data into parameters
  • Generate complex load scenarios to test the scale and performance of API
  • Support all types of services from REST, SOAP to GraphQL

Open API Spec version 3.0 in March 2019, the new feature Swagger Hub Domains was introduced. With this feature, developers can take frequently used objects, path items, response, and store them in separate files to be referenced across multiple different API definitions. These re-usable Domains can be versioned, published, and shared for collaborative feedback among large teams.

Website: Swagger

Pricing: Open-source

11. No one-size-fit-all tools

It hurts, but true!

We believe the list above nominates the best solution available out there if you are planning to adopt API automation testing. However, like most of the solutions in this industry, finding the ideal-one-tool to do it all is almost impossible.

Some may find the features of the commercial players (Postman, Tricentis Tosca, etc.,) are sufficient but the costs of ownership will be the show-stop factor. Open source solutions (Rest-Assured, Karate DSL, etc.,) are affordable but require skilled resources and effort to implement the right frameworks. Tools which seem to be a relative balance between cost and other factors such as Postman, Katalon Studio might have drawbacks to specific project types that need to be considered.

No one-size-fit-all tool

API testing established its trend in automation testing, and more tools will be developed to serve the growing demands of the software development teams. Finding the perfect tool is still tough, but we have the good news that you have way more choices than before. Carefully considering your requirements, pros and cons of each solution — try not too ambitious at the early stage and trial the top 5 relevant candidates from the list above. With the POC for these solutions created, you will have a better knowledge of your project’s critical factors and fine-tune your shortlist. This approach gives you a good chance to identify a suitable tool for the current status and information of the next choice when your project is more mature.

This article was last modified in May 2020 and will be regularly updated with the latest top API testing tools and their functionalities. We love to hear your feedback. Leave a comment below if you have any suggestions on API testing products!

I would love to hear your feedback and let me know if you have other tools to record for the others’ reference.


Related posts:

API Testing Tools

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