My concern here is that this affects users, as it forces them to upgrade diff-lcs to 1.2.2...if they have another gem that depends upon 1.1, it could cause upgrade hindrance.

As for our tests -- we can just write those against the latest version, I think.  Travis will always install the latest version of the dependencies (since we don't keep Gemfile.lock in source control).  We can also add `:pending => (Diff::LCS::VERSION < '1.2.2')` metadata to the tests that depend upon 1.2.2 so that contributors that have an old bundle will just get pending specs for the ones that need the newer version.