Software and APIs go through different stages, from planning, design, implementation, and testing to deployment. All these stages are important as they ensure that the product meets the requirements and is free of errors and bugs. 

SoapUI and Postman are popular API( Application Program Interface ) tools in development. APIs can be used in mobile or web applications as they bridge the web server and the application’s client side. 

APIs come in different forms, such as web, database, system, and File APIs. For instance, if you want to add a weather forecast to your application, you can fetch data from a weather API. Payment processors such as Stripe and PayPal also allow you to use their API to enable the processing of payments. 

This article will introduce the role of SoapUI and Postman tools in API development, discuss the uses of each tool, and check the similarities and differences to help software testers make informed decisions. 

What is SoapUI?

SoapUI is a headless functional testing tool for APIs. You can use SoapUI to test both SOAP and REST APIs. 

What-is-SoapUI

SOAP (Simple Object Access Protocol) services are APIs that use HTTPS/ HTTP as a transport protocol and Extensible Markup Language (XML) as a data format. SOAP APIs are loved for their advanced security features like digital signature verification and message encryption. 

Representational State Transfer (REST) or RESTful is a software architecture that describes how APIs should work. REST APIs should abide by principles such as a uniform interface, a layered system, statelessness, and code on demand. 

SoapUI has these use cases;

Why use SoapUI?

  • Easy to use: SoapUI allows you to generate tests easily through its drag-and-drop, point-and-click features. 
  • Reusable scripts: You don’t have to write scripts for each test case; you can reuse some of your scripts across the entire app. 
  • API functional testing: SoapAPI does comprehensive functional tests to ensure that your app functions as intended always. 
  • Data-driven tests: You can add data to your tests to ensure you get the desired results. 
  • API mocking: SoapUI has a virtualization feature that allows you to mock-test your API before deploying to ensure it works as expected. 
  • Test reporting: SoapUI allows you to generate reports with statistics and metrics for your test cases. 

SoapUI is an open-source tool with free and premium versions. Paid packages start from $659/year. 

What is Postman?

Postman is a testing tool for APIs in REST, SOAP, GraphQL, and JSON formats. You can add this tool to your browser as an extension or download it as a desktop app for Mac, Linux, and Windows. 

The platform has tools for each stage of an application’s lifecycle, from the design, testing, and documentation to mocking. 

Postman has the following use cases;

  • Testing APIs
  • Exploring APIs
  • Documenting APIs
  • Managing APIs
  • Collaborating on APIs

Why use Postman?

  • User-friendly UI: Postman has a simple interface, making it easy for engineers to test their endpoints.
  • Accepts various API formats: You can use Postman to test APIs for almost all web formats. The tool can easily adapt to different standards, protocols, and formats based on your needs. 
  • Various features: You can create, send, and save requests and responses from this Postman. You can also organize these requests and responses into folders and collections. 
  • A central repository: Postman gives developers a central platform to store, catalog, and collaborate in developing APIs. You can store and manage API documentation, specifications, test cases, results, and workflows on this tool. 
  • Enables collaboration: The availability of Postman Workspaces allows team leaders to group engineers into different categories. You can create personal, team, partner, or public workspaces, depending on the nature of the tasks that you want to handle. 
  • Integrates with other tools: Postman has an API that is easy to use. Also, Postman integrates with important tools in the software lifecycle, such as GitHub, Jenkins, and Swagger. Some of the featured integrations are AWS API Gateway, BigPanda, BitBucket Pipelines, and Azure DevOps, to mention a few. 

Postman has a free package that offers tooling and collaboration tools for up to 3 users and paid packages starting from $12/user/month, billed annually.

SoapUI vs. Postman

FeatureSoapUIPostman
RESTful API testingYesYes
SOAP API testingYesYes
DebuggingYesYes
Test script reusabilityYesNo
Automated testingYesYes
CollaborationYesYes
Scripting language JavaScriptGroovy and XML
Security testingYesYes
IntegrationsYesYes

#1. SOAP vs. REST APIs

SOAP and REST are the most common API formats in development. Luckily, SoapUI and Postman support both formats. 

However,  Postman was originally designed for REST APIs but now supports SOAP API testing. 

On the other hand,  SoapUI was originally designed for SOAP APIs but now supports REST API testing.

#2. Debugging

You can debug your code on Postman using the Postman Console. This terminal will show the details of your requests and responses to determine the issues with your code. You can also set breakpoints on the console for easier debugging. 

SoapUI allows you to debug code using the TestCase Debugging feature. You can check your requests and responses by analyzing headers and bodies. You can also set breakpoints to help identify issues. 

#3. Automated tests

Postman’s Collection Runner can automate tests to run a given sequence. You can also schedule tests to run on the Postman cloud. You can also integrate your runs with the Postman CLI and run your tests from the command line. 

The Launch TestRunner feature from SoapUI allows you to write and run test cases. You can also programmatically create and test cases based on various criteria. SoapUI allows you to create and automate tests using scripting languages like Groovy, Python, and Ruby. 

#4. Collaboration

Both tools allow teams to work on the same project effortlessly. 

Postman has a Workspaces feature that allows team leaders to determine team members’ rights. Team members can edit and comment on project files directly from Postman. The tool also supports version control to track changes to project files. 

SoapUI allows team leaders to create shared projects on its platform. Team leaders can then add members to collaborate on API testing. The tool allows commenting and sends notifications whenever a new change is registered on the platform. 

Best Practices for Testing APIs

If you are new to testing, you may be unsure how to conduct such tests. The following are some of the best practices;

  • Plan your tests: You need to be sure why you need tests, what you will be testing, and how to do it. This can only happen when you have a clear plan. 
  • Test with a variety of data: You may be tempted to test your API with only the data you have. Go beyond and test it with invalid outputs and unexpected data to see how it will behave. 
  • Use different testing methods: When prototyping a quick API, you may be tempted to rely only on manual testing. However, you can try others, such as load testing and security testing, to see how your API will behave. 
  • Automate your tests: Automated testing is the way to go if you want to run tests repeatedly.
  • Document your tests: A good API should be well-documented. Document all the test cases and make it easy to reference them in the future. 
  • Invest in continuous improvement: The tests you create as a first-timer might not be comprehensive. Keep improving your tests, which consequently improves your API’s quality. 
  • Track your results: An API is not a one-time thing. Tracking the results makes it easy to determine your API’s performance once it goes live. 

Author’s note

Postman and SoapUI are awesome tools for testing APIs. Each tool has strengths and weaknesses. According to my analysis, the following are some of the cases when you should each tool;

Postman

  • You are new to API testing: Postman has a user-friendly interface, and it is easy to find your way around. 
  • You want to test endpoints manually: You can add headers and bodies to the Postman interface to test your endpoints before you add the data to your database. 
  • You want to test RESTful APIs: Even though Postman tests a wide range of API formats, it was originally designed for REST APIs. 

SoapUI

  • You are experienced in API testing: As an experienced tester, you may find yourself looking for advanced features available on SoapUI. 
  • You want data-rich tests: SoapUI allows you to add data to your tests and get figurative reports. 
  • You are testing SOAP APIs: Even though SoapUI now tests RESTful APIs, it was originally designed for SOAP APIs. 

Conclusion

The choice between SoapUI or Postman will depend on the use case and what you want to achieve. If you are looking for a simple tool for manual and quick tests, Postman will be an awesome choice. However, if you are looking for a comprehensive tool that can offer advanced features such as data-driven testing, load testing, and security testing, SoapUI will be a perfect choice.

If you intend to build an API, check out the best tools for building and testing APIs.