Coinfactorizer Spec

gistfile1.rb

require 'coinfactorizer'

describe Coinfactorizer do
  context "coins" do
    it "changes 0" do
      Coinfactorizer.change(0, Coins).should == {}
    end
    it "changes 1" do
      Coinfactorizer.change(1, Coins).should == {1 => 1}
    end

    it "changes 2" do
      Coinfactorizer.change(2, Coins).should == {1 => 2}
    end

    it "changes 5" do
      Coinfactorizer.change(5, Coins).should == {5 => 1}
    end

    it "changes 6" do
      Coinfactorizer.change(6, Coins).should == {5 => 1, 1 => 1}
    end

    it "changes 10" do
      Coinfactorizer.change(10, Coins).should == {
        10 => 1
      }
    end

    it "changes 31" do
      Coinfactorizer.change(31, Coins).should == {
        25 => 1,
        5 => 1,
        1 => 1
      }
    end
  end

  context "factoring" do
    context "with dependency injected" do
      class MockPrimes
        def self.elements(_)
          [2,3,5,7,11,13,17]
        end

        def self.stop?(total)
          total==1
        end

        def self.destroy_domain_element_from_total(total, domain_element)
          if total == 1
            [1, 0]
          elsif total == 2 && domain_element == 2
            [1, 1]
          elsif total == 3 && domain_element == 3
            [1, 1]
          elsif total == 4 && domain_element == 2
            [1, 2]
          else
            [total, 0]
          end
        end
      end

      it "factors 1" do
        Coinfactorizer.change(1, MockPrimes).should == {}
      end

      it "factors 2" do
        Coinfactorizer.change(2, MockPrimes).should == {2 => 1}
      end

      it "factors 3" do
        Coinfactorizer.change(3, MockPrimes).should == {3 => 1}
      end

      it "factors 4" do
        Coinfactorizer.change(4, MockPrimes).should == {2 => 2}
      end
    end

    context "integration" do
      it "factors 150" do
        Coinfactorizer.change(150, Primes).should == {
          2 => 1,
          3 => 1,
          5 => 2
        }
      end
    end

    describe Primes do
      it "takes factors of 83 from 1" do
        total = 1
        factor = 83
        expectation = [1,0]
        Primes.destroy_domain_element_from_total(total, factor).should == expectation
      end

      it "takes factors of 2 from 2" do
        total = 2
        factor = 2
        expectation = [1, 1]
        Primes.destroy_domain_element_from_total(total, factor).should == expectation
      end

      it "takes factors of 3 from 3" do
        total = 3
        factor = 3
        expectation = [1, 1]
        Primes.destroy_domain_element_from_total(total, factor).should == expectation
      end

      it "takes factors of 2 from 4" do
        total = 4
        factor = 2
        expectation = [1, 2]
        Primes.destroy_domain_element_from_total(total, factor).should == expectation
      end

      it "takes factors of 5 from 75" do
        total = 75
        factor = 5
        expectation = [3, 2]
        Primes.destroy_domain_element_from_total(total, factor).should == expectation
      end
    end
  end
end