Follow-up from "Use Ruby code to determine which migrations to run"

The following discussion from !1413 (merged) should be addressed:

• @toon started a discussion: (+1 comment)

Thanks! rubocop isn't happy though:

spec/lib/gdk/gitlab_rails/db_spec.rb:8:5: C: RSpec/EmptyLineAfterFinalLet: Add an empty line after the last let block.
    let(:shellout_mock) { double('Shellout', stream: nil, success?: true) }
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
spec/lib/gdk/postgresql_spec.rb:48:7: C: RSpec/PredicateMatcher: Prefer using be_db_exists matcher over db_exists?.
      expect(subject.db_exists?('blaat')).to be_truthy
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
spec/lib/gdk/postgresql_spec.rb:71:7: C: RSpec/PredicateMatcher: Prefer using be_in_recovery matcher over in_recovery?.
      expect(subject.in_recovery?).to be_truthy
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
spec/lib/gdk/postgresql_spec.rb:78:7: C: RSpec/PredicateMatcher: Prefer using be_in_recovery matcher over in_recovery?.
      expect(subject.in_recovery?).to be_falsy
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
spec/lib/gdk/postgresql_spec.rb:85:7: C: RSpec/PredicateMatcher: Prefer using be_in_recovery matcher over in_recovery?.
      expect(subject.in_recovery?).to be_falsy
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I've fixed spec/lib/gdk/gitlab_rails/db_spec.rb but I'm not a fan of RSpec/PredicateMatcher as it makes tests harder to read so am going to disable in another MR 🙂

 @ashmckenzie I'm back, this time with some specs.