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require "librarian/algorithms"
module Librarian
module Algorithms
describe AdjacencyListDirectedGraph do
describe 'cyclic?' do
subject(:result) { described_class.cyclic?(graph) }
context "with an empty graph" do
let(:graph) { { } }
it { should be false }
end
context "with a 1-node acyclic graph" do
let(:graph) { { ?a => nil } }
it { should be false }
end
context "with a 1-node cyclic graph" do
let(:graph) { { ?a => [?a] } }
it { should be true }
end
context "with a 2-node no-edge graph" do
let(:graph) { { ?a => nil, ?b => nil } }
it { should be false }
end
context "with a 2-node acyclic graph" do
let(:graph) { { ?a => [?b], ?b => nil } }
it { should be false }
end
context "with a 2-node cyclic graph" do
let(:graph) { { ?a => [?b], ?b => [?a] } }
it { should be true }
end
context "with a 2-scc graph" do
let(:graph) { { ?a => [?b], ?b => [?a], ?c => [?d, ?b], ?d => [?c] } }
it { should be true }
end
end
describe 'feedback_arc_set' do
subject(:result) { described_class.feedback_arc_set(graph) }
context "with an empty graph" do
let(:graph) { { } }
it { should be_empty }
end
context "with a 1-node acyclic graph" do
let(:graph) { { ?a => nil } }
it { should be_empty }
end
context "with a 1-node cyclic graph" do
let(:graph) { { ?a => [?a] } }
it { should be == [[?a, ?a]] }
end
context "with a 2-node no-edge graph" do
let(:graph) { { ?a => nil, ?b => nil } }
it { should be_empty }
end
context "with a 2-node acyclic graph" do
let(:graph) { { ?a => [?b], ?b => nil } }
it { should be_empty }
end
context "with a 2-node cyclic graph" do
let(:graph) { { ?a => [?b], ?b => [?a] } }
it { should be == [[?a, ?b]] } # based on the explicit sort
end
context "with a 2-scc graph" do
let(:graph) { { ?a => [?b], ?b => [?a], ?c => [?d, ?b], ?d => [?c] } }
it { should be == [[?a, ?b], [?c, ?d]] }
end
end
describe 'tsort_cyclic' do
subject(:result) { described_class.tsort_cyclic(graph) }
context "with an empty graph" do
let(:graph) { { } }
it { should be == [] }
end
context "with a 1-node acyclic graph" do
let(:graph) { { ?a => nil } }
it { should be == [?a] }
end
context "with a 1-node cyclic graph" do
let(:graph) { { ?a => [?a] } }
it { should be == [?a] }
end
context "with a 2-node no-edge graph" do
let(:graph) { { ?a => nil, ?b => nil } }
it { should be == [?a, ?b] }
end
context "with a 2-node acyclic graph" do
let(:graph) { { ?a => [?b], ?b => nil } }
it { should be == [?b, ?a] } # based on the explicit sort
end
context "with a 2-node cyclic graph" do
let(:graph) { { ?a => [?b], ?b => [?a] } }
it { should be == [?a, ?b] } # based on the explicit sort
end
context "with a 2-scc graph" do
let(:graph) { { ?a => [?b], ?b => [?a], ?c => [?d, ?b], ?d => [?c] } }
it { should be == [?a, ?b, ?c, ?d] }
end
# Dependencies are sorted alphabetically. Should they?
context "should be deterministic" do
let(:graph) { { ?a => [], ?b => [?c], ?c => [] } }
it { should be == [?a, ?c, ?b] }
end
context "should be deterministic" do
let(:graph) { { ?c => [], ?b => [?a], ?a => [] } }
it { should be == [?a, ?b, ?c] }
end
end
end
end
end
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