life.rb

# Life:
# Rule 1: Any live cell with fewer than 2 live neighbors dies
# Rule 2: Any live cell with more than 3 live neighbors
# Rule 3: Any live cell with two or three live neighbors lives on
# Rule 4: Any dead cell with exatctly three live cells becomes a live cell

require "rspec/given"

describe "grid" do
  Given(:grid) { Grid.new(input) }

  context "a dead 3 by 3 grid" do
    Given(:input) { "...\n...\n..." }
    When { grid.step }
    Then { grid.to_s.should == input }
  end

  context "a 3 by 3 with only one cell" do
    Given(:input) { "...\n.*.\n..." }
    When { grid.step }
    Then { grid.to_s.should == "...\n...\n..." }
  end

  context "a 3 by 3 with two live cells" do
    Given {pending}
    Given(:input) { "...\n***\n..." }
    When { grid.step }
    Then { grid.to_s.should == "...\n.*.\n..." }
  end

  context "a 3 by 3 with four live cells" do
    Given(:input) { "...\n**.\n**." }
    When { grid.step }
    Then { grid.to_s.should == input }
  end
end

class Grid
  LIVE = '*'
  DEAD = '.'

  def initialize(grid)
    @grid = grid.split("\n").map { |row_str| row_str.split(//) }
  end

  def step
    
  end

  def to_s
    @grid.map { |row| row.join }.join("\n")
  end

end