describe Nanoc::Int::Errors::DependencyCycle do
  subject(:error) { described_class.new(graph) }

  let(:graph) do
    Nanoc::Int::DirectedGraph.new([]).tap do |g|
      g.add_edge(rep_a, rep_b)
      g.add_edge(rep_b, rep_c)
      g.add_edge(rep_c, rep_d)
      g.add_edge(rep_d, rep_e)
      g.add_edge(rep_e, rep_b)
    end
  end

  let(:rep_a) { Nanoc::Int::ItemRep.new(Nanoc::Int::Item.new('a', {}, '/a.md'), :default) }
  let(:rep_b) { Nanoc::Int::ItemRep.new(Nanoc::Int::Item.new('b', {}, '/b.md'), :default) }
  let(:rep_c) { Nanoc::Int::ItemRep.new(Nanoc::Int::Item.new('c', {}, '/c.md'), :default) }
  let(:rep_d) { Nanoc::Int::ItemRep.new(Nanoc::Int::Item.new('d', {}, '/d.md'), :default) }
  let(:rep_e) { Nanoc::Int::ItemRep.new(Nanoc::Int::Item.new('e', {}, '/e.md'), :default) }

  it 'has an informative error message' do
    expected = <<EOS
The site cannot be compiled because there is a dependency cycle:

    (1) item /e.md, rep :default, uses compiled content of
    (2) item /d.md, rep :default, uses compiled content of
    (3) item /c.md, rep :default, uses compiled content of
    (4) item /b.md, rep :default, uses compiled content of (1)
EOS

    expect(error.message).to eql(expected)
  end
end