How to run unit-tests in all browsers?

I've never used Selenium but I guess it's for simulating user interaction in all browsers.

That's like integration tests.

But how do you test your js libraries/frameworks (unit testing) on all the browsers in an automated way?

For unit-testing you can try http://code.google.com/p/js-test-driver/

JsTestDriver consist of a single JAR file which contains everything you need to get started. For in depth discussion of command line option see GettingStarted.

Here is an overview of how JsTestDriver works at runtime...

You can have a look at TestSwarm:

project that I’m working on: TestSwarm...

Its construction is very simple. It’s a dumb JavaScript client that continually pings a central server looking for more tests to run. The server collects test suites and sends them out to the respective clients.

All the test suites are collected. For example, 1 “commit” can have 10 test suites associated with it (and be distributed to a selection of browsers)...

The nice thing about this construction is that it’s able to work in a fault-tolerant manner. Clients can come-and-go. At any given time there might be no Firefox 2s connected, at another time there could be thirty. The jobs are queued and divvied out as the load requires it. Additionally, the client is simple enough to be able to run on mobile devices (while being completely test framework agnostic)...

The best one imo is the one from YUI : http://developer.yahoo.com/yui/3/test/ But doing unit-testing in every browser is kind of hard... Most people just test with it during development and just use node.js to test later on in case they broke something.

As the referenced post in a previous article suggests, you could use js-test-driver. Its specifically for JavaScript unit testing across multiple browsers, exactly what you want. I have messed around with it and it is pretty good. I haven't done any serious commercial testing in it though.