Make dependency explicit so test can be run in isolation.
Make dependency explicit so test can be run in isolation.

I was seeing the following error occur a number of times when trying to
run `GovspeakTest` on its own :-

    NameError: uninitialized constant GovspeakTest::OpenStruct

alphagov/govspeak,alphagov/govspeak,met-office-lab/govspeak,met-office-lab/govspeak