To avoid being able to introduce dependencies between tests this commit
makes sure that we close the document between tests so that we can't
accidentally rely on state set by a previous test.
Over time the number of integration tests that get the rectangle for a
given selector has increased quite a bit, and the code to do so has
consequently become duplicated.
This commit refactors the integration tests to move the rectangle
fetching code to a single place, which reduces the code by over 400
lines and makes the individual tests simpler.
