gistfile1.rb

###
#
# This is a dirty, dirty trick to write tests that test `require`:
#
module RequireMock
  REQUIRE_SENTINEL = []

  def require(lib)
    REQUIRE_SENTINEL << lib
    super
  end
end
Object.send(:include, RequireMock)

def require_lib(lib)
  ->(block) do
    REQUIRE_SENTINEL.clear
    block.call
    REQUIRE_SENTINEL.include?(lib)
  end
end

# ...

describe Peacekeeper::Model do
# ...
  describe 'manages a data source selection' do
    it 'is nil by default' do
      Peacekeeper::Model.data_source.should.be.nil
    end

    describe 'set to Sequel' do
      it 'requires the Sequel library' do
        -> { Peacekeeper::Model.data_source = :sequel }.should require_lib('sequel')
      end
# ...
    end
  end
end