gistfile1.rb

require "spec_helper"

describe AdjacencyMatrix do

  context "undirected graph" do
    let(:pitt2pitt) {
      AdjacencyMatrix.connections({"Pittsburgh" => "Pittsburgh"}, false)
    }
    let(:pitt2clev) {
      AdjacencyMatrix.connections({"Pittsburgh" => "Cleveland"}, false)
    }

    describe "#connection_exists?" do
      it "should return true if a connection exists" do
        pitt2pitt.connection_exists?("Pittsburgh", "Pittsburgh").should be_true

        pitt2clev.connection_exists?("Pittsburgh", "Cleveland" ).should be_true
        pitt2clev.connection_exists?("Cleveland",  "Pittsburgh").should be_true
      end

      it "should return false if a connection doesn't exist" do
        pitt2pitt.connection_exists?("Pittsburgh", "Cleveland" ).should be_false

        pitt2clev.connection_exists?("Pittsburgh", "Pittsburgh").should be_false
        pitt2clev.connection_exists?("Cleveland",  "Cleveland" ).should be_false
      end
    end

    describe "#incoming_connections" do
      it "should return the number of incoming connections" do
        pitt2pitt.incoming_connections("Pittsburgh").should == 1

        pitt2clev.incoming_connections("Pittsburgh").should == 1
        pitt2clev.incoming_connections("Cleveland" ).should == 1
      end
    end

    describe "#outgoing_connections" do
      it "should return the number of outgoing connections" do
        pitt2pitt.outgoing_connections("Pittsburgh").should == 1

        pitt2clev.outgoing_connections("Pittsburgh").should == 1
        pitt2clev.outgoing_connections("Cleveland" ).should == 1
      end
    end
  end

  context "directed graph" do
    let(:pitt2pitt) {
      AdjacencyMatrix.connections({"Pittsburgh" => "Pittsburgh"})
    }
    let(:pitt2clev) {
      AdjacencyMatrix.connections({"Pittsburgh" => "Cleveland"})
    }
    let(:pitt2clev2chic) {
      AdjacencyMatrix.connections({"Pittsburgh" => "Cleveland",
                                   "Cleveland"  => "Chicago"})
    }

    describe "#connection_exists?" do
      it "should return true if a connection exists" do
        pitt2pitt.connection_exists?("Pittsburgh", "Pittsburgh").should be_true

        pitt2clev.connection_exists?("Pittsburgh", "Cleveland" ).should be_true
      end

      it "should return false if a connection doesn't exist" do
        pitt2clev.connection_exists?("Pittsburgh", "Pittsburgh").should be_false
        pitt2clev.connection_exists?("Cleveland",  "Pittsburgh").should be_false
        pitt2clev.connection_exists?("Cleveland",  "Cleveland" ).should be_false
      end
    end

    describe "#row" do
      it "should return the row of an item" do
        pitt2pitt.row("Pittsburgh").should == [1]

        pitt2clev.row("Pittsburgh").should == [0, 1]
        pitt2clev.row("Cleveland" ).should == [0, 0]
      end
    end

    describe "#column" do
      it "should return the column of an item" do
        pitt2pitt.column("Pittsburgh").should == [1]

        pitt2clev.column("Pittsburgh").should == [0, 0]
        pitt2clev.column("Cleveland" ).should == [1, 0]
      end
    end

    describe "#incoming_connections" do
      it "should return the number of incoming connections" do
        pitt2pitt.incoming_connections("Pittsburgh").should == 1

        pitt2clev.incoming_connections("Pittsburgh").should == 0
        pitt2clev.incoming_connections("Cleveland" ).should == 1
      end
    end

    describe "#outgoing_connections" do
      it "should return the number of outgoing connections" do
        pitt2pitt.outgoing_connections("Pittsburgh").should == 1

        pitt2clev.outgoing_connections("Pittsburgh").should == 1
        pitt2clev.outgoing_connections("Cleveland" ).should == 0
      end
    end

    context "squaring the matrix when the longest link == 1" do
      let(:sqrd) { pitt2clev ** 2 }

      it "should negate all connections" do
        sqrd.connection_exists?("Pittsburg", "Cleveland").should be_false
      end
    end

    context "squaring the matrix when the longest link == 2" do
      let(:sqrd) { pitt2clev2chic ** 2 }

      it "should negate connections of length 1" do
        sqrd.connection_exists?("Pittsburgh", "Cleveland").should be_false
        sqrd.connection_exists?("Cleveland",  "Chicago"  ).should be_false
      end

      it "should keep connection of length 2" do
        sqrd.connection_exists?("Pittsburgh", "Chicago").should be_true
      end
    end
  end

end