This is the reverse of the way these tests are usually written, and I think this way is somewhat weaker: you're not checking whether commenting produces any reasonable output, just that uncommenting afterward cleanly reverts whatever that output was.  Most usages of testToggleBlock() don't invoke EDIT_BLOCK_COMMENT manually beforehand, so testToggleBlock() does a comment-uncomment pair (rather than uncomment-comment as here), and those tests pass an explicit expected value for the commented text.