Load Testing Using loadUI – A Free and Open Source Load Testing Tool

What is loadUI?

LoadUI is a free and open source load testing tool that allows you to do complex load tests and test the performance by simply dragging the different components around. LoadUI lets you create and update test cases while you run them. What is making loadUI powerful is the focus on usability through its visual interface and intuitive design combined with the flexibility that comes from the possibility of making changes during the test.

How loadUI works:

LoadUI consist of building blocks called Components that you drag from the

Component Toolbar to the Project you’re working on. These components connect to each other by wires and there is no limit for how many components that you can create and connect.

This way of drag-and-drop testing is especially useful during the test since you can do complex load tests. The overview that you get makes it easier to try different combinations during the actual test and react to them immediately. In loadUI, Instant feedback is king.

Creating load tests in loadUI:

In order to run a test in loadUI you need at least two components (and an empty Project to work in);

– A generator

Which creates a load, for example, 100 requests per second.

– A Runner

That runs a certain type of test, for example, a web test.

So let’s do it; drag out a Fixed Rate Generator and a Web Page Runner.

You can’t run them yet though first, you need to connect them. You do this by connecting the nodes, or terminals, located above and below the components to each other with connections.

So now connect the Fixed Rate Generator to the Web Page Runner.

Now that everything is connected you should enter what website you want to load test into the Web Page Runner. Your test is now ready to run! Click the play button in the top menu to make your generator start sending requests to your site.

You can now follow, in real-time, how the test is going by clicking the Results Workbench button. Once there, double-click on your Current Run and, from the left-hand menu, drag-out Response Time to the rack.

Congratulations! You have now created your first load test in loadUI. Play around with the widgets you have on your dashboard, experiment by adding some more and try tracking other values in the Results Workbench. A good next step would to add an Assertion component and connect it to the Web Page Runner. Then you can, for example, test how many times you your requests come through while following certain rules you set up (like taking less than 10 milliseconds).

Pro Tips:

Let a manager test!

This is the modern way of gorilla testing.  Let someone less proficient do the testing for you and see what breaks your service. It will also create an understanding and passion for testing within the management. A usual comment is “This is fun! But hard…”

It’s interactive, use it!

LoadUI is highly interactive and configurable in real-time, so take advantage of that.

Create a second test in real time on the same server with a different Generator and see if the system shows weaknesses when exposes to chaotic, life-like, behaviour. Change this in real time and experiment.

Record your tests

Since loadUI is so interactive, reproducing the tests can be difficult. Use a screen recorder like Wink (which is free) to be able to replay your tests and see what caused the service to crash.

Work structured

LoadUI has support for test cases. Break up your tests into smaller test cases; you can always start them all at once.

Don’t double-work

If you have created functional tests in soapUI, you can simply run these in loadUI with the soapUI component. This way you don’t have to redefine the test another time in loadUI.

Write your own component

LoadUI is not only free; it’s open-source, too. That means that you can write your own components, in Groovy, if you wish. Only you set the limits for what is possible in LoadUI! Read more about creating your own components here.

Read more about loadUI, and download it here: Latest loadUI version


This is a guest article by Henrik Olsson.

About Author:

Henrik is a software developer for loadUI from Stockholm, Sweden with an academic background in Distributed Systems and a passion for usability. He is experienced in teaching and thinks that most things can be easily explained, if well modelled and accurately targeted.

Editor’s Note:

I’m glad to share this open source load testing tool with my readers. LoadUI and soapUI are the best open source software testing tools from trusted company eviware (now SmartBear). If you are thinking to introduce load testing tool on your project try loadUI and soapUI (functional testing tool).  Also, I personally used soapUI for many projects and will soon cover it in a separate article. I love the power and beauty of these open source tools!

If you used this tool and have some tips to share, please do it in below comment section. Also, we would be happy to hear and answer your queries on loadUI.