I think I'd prefer to see the `:should` syntax disabled for _all_ of the specs in this file.  I can't think of a way that having the `:should` syntax enabled would break it, but there are many branches and code paths to the implementation of `RSpec::Mocks::StubChain` and it would give me greater confidence that it works for all of them if `:should` is disabled for all the specs in this file.  Or, if you do want to test that it works with `:should` enabled, that's fine -- just flip it so that there's only one test where it is enabled and all the rest where is is disabled.