API testing (Application Programming Interface Testing) is a software testing type which 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 test 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.
1. 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:
- Create test quickly and easily with Drag and drop, Point-and-click
- Quickly create custom code using Groovy
- 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 asynchronous testing
- Reusability of Scripts: load tests and security scans can be reused for functional test cases in a just several steps
Website: https://www.soapui.org/
2. Postman
Being originally a Chrome browser plugin, Postman now extends their solution with the native version for both Mac and Windows.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: https://www.getpostman.com/
3. Katalon Studio
Katalon Studio is a free automation test tool provide 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 request 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 data-driven approach.
- Can be used for both automated and exploratory testing.
- Suitable for both pros and non-techies
Website: https://www.katalon.com
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
Website: https://www.tricentis.com/
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.
- 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.
Website: https://apigee.com/api-management/
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
Website: https://jmeter.apache.org/
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 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
Website: http://rest-assured.io/
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
Website: https://assertible.com/
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
Website: https://github.com/intuit/karate
10. No one-size-fits-all tools
The above list is a round-up of some of the best API testing tools. 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 trialing the top 5 relevant candidates from the list above which are a good summary of the best API testing tools. 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 the suitable tool for the current status and information of the next choice when your project is more mature.
