Creating the hosts without specifying their site means that the factory will create a site for each of them which we don't need, and 2 extra hosts are created somehow as well. Doing it like this creates only the site and two hosts we need for this test:

    let(:site) { create :site_without_host }

    before do
      create(:host, hostname: 'aka.f.com', site: site)
      create(:host, hostname: 'www.f.com', site: site)
    end

    subject(:default_host) do
      site.default_host
    end