heptagonal_spec.rb

describe Integer, "#heptagonal?" do
  # A000566
  @seq = [0,1,7,18,34,55,81,112,148,189,235,286,342,403,
          469,540,616,697,783,874,970,1071,1177,1288,1404,
          1525,1651,1782,1918,2059,2205,2356,2512,2673,2839,
          3010,3186,3367,3553,3744,3940,4141,4347,4558,4774,
          4995,5221,5452,5688].to_seq

  @seq.each do |n|
    it "returns true for heptagonal number #{n}" do
      n.should be_heptagonal
    end
  end

  @seq.invert.sample(10).each do |n|
    it "returns false for non-heptagonal number #{n}" do
      n.should_not be_heptagonal
    end
  end
end