Test

prime_numbers.rb

#!/usr/bin/env ruby

class FirstTenPrimeNumbersMath 
  
  def prime_numbers
    [2, 3, 5, 7, 11, 13, 17, 19, 23, 29] 
  end

  def multiply(first_number, second_number)
    if are_integers?(first_number, second_number)
      first_number * second_number
    else
      "Only integers are allowed"
    end
  end

  def are_integers?(first_number, second_number)
    first_number.is_a? Integer and second_number.is_a? Integer
  end

  def multiply_row_by_number(number)
    prime_numbers.inject([]) {|array, prime_number| array << multiply(number, prime_number)}
  end
end

class TablePresenter

  def dashes
    "---------------------------------------------"
  end

  def first_row
    dashes+"\n"
  end

  def header_string(string)
    string
  end

  def header(string)
    first_row + header_string(string) + "\n" + first_row
  end

  def footer
    dashes
  end

  def format_element(number)
    number.to_s+"|"
  end

  def format_row(array)
    array.inject("|") {|string, element| string += format_element(element)}
  end

  def format_column(array)
    array
  end
end

class PrimesTable
  attr_accessor :prime_numbers, :table_presenter

  def initialize(prime_numbers, table_presenter)
    @prime_numbers = prime_numbers
    @table_presenter = table_presenter
  end

  def format_table
    puts @table_presenter.header("Times 10 Primes")
    @prime_numbers.prime_numbers.each do |prime_number|
      puts prime_number.to_s + @table_presenter.format_row(@prime_numbers.multiply_row_by_number(prime_number))
    end
    puts @table_presenter.footer
  end

end

primes_table = PrimesTable.new(FirstTenPrimeNumbersMath.new, TablePresenter.new)
primes_table.format_table

prime_numbers_spec.rb

require 'minitest/spec'
require 'minitest/autorun'
require './prime_numbers.rb'

describe FirstTenPrimeNumbersMath do
    before(:each) do
      @prime_numbers = FirstTenPrimeNumbersMath.new
    end
    it 'must have method prime_numbers' do
      @prime_numbers.prime_numbers.must_equal [2, 3, 5, 7, 11, 13, 17, 19, 23, 29] 
    end
    it 'wont include zero' do
      @prime_numbers.prime_numbers.wont_include 0
    end
    it 'must multiply correctly' do
      @prime_numbers.multiply(2, 2).must_equal 4
    end
    it 'must multiply only integers' do
      @prime_numbers.multiply('as', 1).must_equal "Only integers are allowed"
    end
    it 'must multiply first row' do
      @prime_numbers.multiply_row_by_number(2).must_equal [4, 6, 10, 14, 22, 26, 34, 38, 46, 58]
    end
end

describe TablePresenter do
  before(:each) do
    @table = TablePresenter.new
  end

  it 'must print table header' do
    @table.header_string('Times 10 Primes').must_equal "Times 10 Primes"

  end
  it 'must print table footer' do
    @table.footer.must_equal "---------------------------------------------"

  end

  it 'must print not first element with proper format' do
    @table.format_element(2).must_equal "2|"
  end

  it 'must format row' do
    @table.format_row([1,2,3]).must_equal "|1|2|3|"
  end
end

describe PrimesTable do
  before(:each) do
    @prime_numbers = FirstTenPrimeNumbersMath.new
    @table = TablePresenter.new
    @primes_table = PrimesTable.new(@prime_numbers, @table)
  end

  it 'must have prime_numbers and table_presenter methods' do
    @primes_table.prime_numbers.methods.must_include(:multiply)
    @primes_table.table_presenter.methods.must_include(:first_row)
  end
end

Rakefile

require 'rake/testtask'

Rake::TestTask.new do |t|
  t.libs.push "lib"
  t.test_files = FileList['*_spec.rb']
  t.verbose = true
end