Is it possible to share GL contexts among multiple canvas elements on the same page? If so, how - is it done by default?

Also, what approach do you recommond for unit testing where each test uses a new GL context? Currently, I am using the Jasmine framework and have each test (or sometimes group of tests) dynamically create and destroy a canvas element with document.createElement, document.body.appendChild, and document.body.removeChild. Firefox seems to cleanup reasonably well, but I've gotten Chrome to choke more than a few times.