If the web application is viewable in a browser, then eValid can test it -- regardless of where it is hosted.
We have done tests of SalesForce CRM before, as well as for such similar systems as Microsoft Dynamics and SAP.
No problem at all.
The fact that the web application is in the cloud doesn't affect how it is viewed in a browser.
And, it goes the other way too: You can test a cloud-based application from the cloud, using cloud-based machines.
This is the way we get performance test runs involving 1,000's "browser users." Using cloud machine resources.
eValid Support Team