Constrain a value between two values

numeric_extensions.rb

class Numeric
  def between( *values )
    low = values.min
    high = values.max
    [[low,self].max, high].min
  end
end

require "test/unit"
require "shoulda"

class TestNumericExtensions < Test::Unit::TestCase
  context "An integer" do
    setup do
      @target = 8
    end
    
    should "give the same results if the low and high values come in a different order" do
      assert_equal @target, @target.between(16, 4)
    end
    
    should "give the same results if there are three values, not two" do
      assert_equal @target, @target.between(4, 16, 32 )
    end
    
    context "greater than the lowest value" do
      setup do
        @low = 4
      end
      
      context "and less than the highest value" do
        setup do
          @high = 16
        end
        
        should "be between the two, and return itself" do
          assert_equal(@target, @target.between( @low, @high ))
        end
      end
    end

    context "less than the lowest value" do
      setup do
        @low = 16
      end
      
      context "and less than the highest value" do
        setup do
          @high = 32
        end
        
        should "be less than all, and return the lowest" do
          assert_equal @low, @target.between( @low, @high )
        end
      end
    end

    context "greater than the lowest value" do
      setup do
        @low = 4
      end
      
      context "and greater than the highest value" do
        setup do
          @high = 6
        end
        
        should "be greater than all, and return the high" do
          assert_equal @high, @target.between( @low, @high )
        end
      end
    end
  end
end