Should we run unit tests in the cloud before CI?

Imagine if you could push your current branch to a test server and have it automatically run all of your unit tests!

You could get feedback on your entire test suite in a few minutes, rather than waiting for a lengthier CI process, which might take up to ~20 minutes (depending on the infrastructure and setup in your organisation).

Several automation test platforms now exist, to perform cloud testing on longer-running end-to-end tests. These include Selenium Grid, TestingBot and BrowserStack.

Why not extend this kind of service also to unit tests?

Advantages of cloud-based unit test execution over CI:

• CI can be time-consuming, if it runs a full build, linting, type-checking and other operations. Cloud-based unit testing lets us isolate just the tests.
• CI tends to be monitored on a separate web-page. Cloud-based unit testing (in theory) could be integrated directly into the developer's IDE, so it would feel similar to running the tests locally.

Advantages of cloud-based unit test execution over local:

• When working with a very large code base, with a large number of tests, and not well de-coupled, we might want to run all the tests. An optimised cloud environment might be able to do this faster than a dev box, and without consuming resources which could cause our IDE and other tools to slow down.

So far I don't know of any platforms that actually do this, but perhaps the aforementioned automation testing platforms could be configured/tweaked to enable it.

What do you think?