Testing query parameter without value in SoapUI - how can I do this?

[segreat]

For instance, if I want to test the following URL:

GET http://example.com?api=testAPI&$metadata

How can I append the $metadata to the URL without adding a value to it? It won't work if it has a value.

[nmrao]

For Open Source Edition, here is extension for events
https://github.com/nmrao/soapuiExtensions