Postman, Katalon Studio, and REST Assured are excellent tools for automated API testing. Speeding up testing and increasing efficiency, they have certain advantages and disadvantages when it comes to the practical side. Let’s find out which tool and in what situation can best fit your testing objectives.

Easy start with Postman

This tool is a good option for beginners in mastering API automation testing.
You’ll need a basic JavaScript knowledge to write tests. Postman also provides a standard set of snippets for immediate use. Due to its speed, Postman can be used as a backup tool for quick requests sending and response receiving.

To its pros we can refer:

• Short learning curve before starting automation testing.
• Easy-to-use UI.
• Growing community.
• Smooth work across all desktop platforms.
• Operation speed.
• Opportunity to create a workspace, cloud storage, etc.
• Tests start from the command line.
• Traffic interception from mobile devices.

To cons:

• It works solely with JavaScript.
• You cannot set up fully-featured automation with files upload on a server.
• Prepared in advance request templates cannot be reused.
• You cannot build up an intelligent project structure for the increased number of tests.
• No opportunity to conduct a debugging using breakpoints.

Full automation with Katalon Studio

If you’re planning to focus on a fully-fledged automated API testing, Katalon Studio will help you to cope with the task. Although this tool requires a basic Groovy or Java knowledge, it’s one of the best solutions for writing parameterized tests.

Katalon Studio is indeed a relatively new tool, some improvements should be still implemented, and its enhancement speed isn’t fast.

However, there are more pros than cons we’ve encountered using this solution.

Pros:

• Longer learning curve than with Postman. You need to have a basic understanding of the automation process and experience with IDE.
• Full-scale automation of API testing.
• Groovy, Java, and the GUI builder for test writing.
• Option of custom methods (keywords) creation with their further usage in tests.
• Opportunity to work with different variables and profiles.
• Comprehensive parameterized tests.
• Embedded reports support and email distribution system for reports.
• Mature debug mode.

Cons:

• Slow application performance.
• No consistently operating version for Linux.
• Recurrent tests’ crashes for no apparent cause.

Widely used REST Assured

To write automated tests of different complexity, utilizing the advantages of - Java or Groovy, you can use one of the most popular Java-libraries REST Assured.
This tool is a must for automated API testing as it doesn’t have any limitations and can be combined with different frameworks.

This library provides an option of writing any tests and performing any manipulations with data during the testing process leaving tests independent from the software under check.

Pros of REST Assured are the following:

• Opportunity to apply ready-made tools without connecting additional libraries.
• Comprehensive documentation is available on Github.
• Extensive testing options in combination with different frameworks for testing and reports building.
• Tests writing in the form of code using Java or Groovy with an option to update, improve the code’s quality or the number of tests.
• Independence from the platform or development environment.

Cons:

• The necessity of having a basic knowledge of Java, Groovy, Maven and the experience of working with dependencies, command line and IDE.
• Code quality and time necessary for compilation directly impact test running speed.
• No GUI as for Postman and Katalon Studio.
• A tester has to connect and set up additional tools for reports building.
• It will take some time to check general API working efficiency and spend time on test writing.

Bottom line

Each of the described above tools can fully cope with the assigned tasks but in his own way.

Speaking about the practical side and our experience, we’d recommend a variant of combining REST Assured with JUnit 5, Hamcrest, Allure, and Maven for an effective automated API testing. Postman will perfectly cope with quick requests sending, and responses checking.

Do you have experience of working with these tools? Maybe you can advise other solutions for automated API testing?