console_printer_spec.rb

describe TTT::ConsolePrinter
  subject{TTT::ConsolePrinter.new(output)}
  let(:output) {StringIO.new("")}
  let(:board) {...}

  it "should be awesome" do
    subject.print(board)
    expect(output.read).to eq("An awesome TTT board")
  end
end

ttt-console_printer.rb

module TTT
  class ConsolePrinter
    def initialize(output)
      @output = output
    end

    def print(board)
      @output.puts "An awesome TTT board"
    end
  end
end

ttt.rb

output = TTT::ConsolePrinter.new($STDOUT)