Interest in Application Programming Interface (API) testing is rising steadily over the last couple of years, majorly because of its effectiveness towards optimizing cost and reduced time-to-market. Researchers from Smartbear highlights how API testers automated their tests by 50% in 2017, and this number is expected to grow by 30% in 2019.

Often, API testing can be challenging, if you aren’t sure where to start, it’s vital for you to understand what’s API Testing and how to test your APIs to ensure its success. It’s even more complicated because APIs are based on several protocols and standards, that we often don’t meet in other forms of testing.

What’s API Testing?

It’s a software testing type which focuses on the developed APIs that meets expectations regarding the functionality, reliability, performance, scalability, and security of an application.

Best Practices for API Testing

Before you head off and get started with API testing, here are the top tips you can implement before the test to ensure better success:

  • Test for the expected results first
  • Add stress to the system through a series of API load tests
  • Prioritize API function calls to test more efficiently
  • Limit the tests by keeping it as isolated as possible
  • Create test cases for all possible API input combinations

Top Three API Testing Tools

Here are the top API testing tools covering open-source and commercial solutions that you can leverage to best suit your needs.

1. SoapUI
Soap UI is a dedicated tool for API testing. With its improved interface and features, you can immediately switch to SoapUI as it is quite seamless as it can get.


  • It’s time effective and language independent
  • It has easy an syntax which makes the tests easier to write and read
  • Incorporates advanced functionality into your API tests without complex scripting or multi-level navigation
  • Advanced security testing capabilities

2. Postman
Postman was primarily a Chrome browser plugin, and now they extend their solution with the native version for both Mac and Windows.


  • Builds, test, and document your APIs faster
  • The rich interface that makes it easy to navigate
  • Chain requests so that you can use the first request’s response in the next
  • Stores information for running tests in a different environment
  • Possesses run, test, document, and monitoring features

3. Newman

Newman is the Postman’s collection runner engine that sends API requests and receives the response to run your tests against the response. It can be easily integrated with Jenkins, AppVeyor, Bamboo, CodeShip, Travis CI, Circle CI, or any other code deployment pipeline tool.


  • Built to easily integrate with your continuous integration servers and systems
  • Creates a collection of API endpoints and calls for them whenever you wish to see responses
  • Allows user to run Postman collections from command line
  • Improve the predictability of tests conducted and manipulates and receives data in different ways
  • Reports generated provides information about the current collection run in a format that’s easy and accessible

API Testing Can Give You a Competitive Edge
API testing provides a host of advantages that improve the coverage of your test cycle, conserves resources and results in faster and efficient releases.

  1. Test for Core Functionality: Exposes minor errors that often-become large problems during Graphical User Integration (GUI) testing. It enables testing in sync with development, fostering communication and improved collaboration between teams
  2. Time Effective: API testing requires less code and thus provides better, faster test coverage than automated GUI tests. This results in faster time-to-market and reduced testing cost
  3. Language Independent: Data is exchanged using XML or JSON, and these modes are completely language-independent that allows the user to select any core language when pursuing testing services
  4. Easy Accessibility and Integration: Highly integrable tests are possible, easy integration further allows to create new users within the application


At WinWire, we combine automation with intelligence to help enterprises deliver products and services that are error-free and in-sync with customer expectations. We offer the full spectrum of software QA services by leveraging the best of API Testing tools and help customers accelerate time-to-market and address performance challenges while minimizing costs.

Sr. QA Engineer