Singleton Pattern

Note: This is a class activity, nothing needs to be delivered.

Create a folder called singleton. Inside this folder, create two files called: tigger.rb and tigger_test.rb.
You are given the following Ruby class that models the famous Tigger character from A. A. Milne's “Winnie The Pooh” books:
```
# File: tigger.rb

class Tigger

  def to_s
    return "I'm the only one!"
  end

  def roar
    'Grrr!'
  end

end
```
Convert this class into a singleton using whatever technique you find fit. Place the resulting class in the tigger.rb source file.

Check your solution using the following test case (place the test in the source file tigger_test.rb):

# File: tigger_test.rb

require 'minitest/autorun'
require 'tigger'

# If you get a NameError saying that Minitest is an 
# uninitialized constant, replace Minitest::Test with
# MiniTest::Unit::TestCase
class TiggerTest < Minitest::Test


  def test_tigger
    t = Tigger.instance
    assert_same(t, Tigger.instance)
    assert_raises(NoMethodError) do # "new" method should be private!
      Tigger.new
    end
    assert_equal("I'm the only one!", t.to_s)
    assert_equal('Grrr!', t.roar)
  end

end

S/W Design and Architecture

Singleton Pattern