Extend expect_length to use an S4 object's length method, if exists #564
This pull request extends
This pull request also contains a commit that updates the junit test fixture for what I am guessing is a change in the 'xml2' package. When I reset my fork to upstream/master, it failed on Travis. I suspect an 'xml2' change caused the failure because the most recent release of that package was after the most recent commit to the master branch of 'testthat'.