test_core_arithmetic.rb

require 'rspec'
require './../core_arithmetic'

class DataSet < Array

  def input(data)
    if data.kind_of?(Enumerable)
      data.each do |item|
        if item.kind_of?(Numeric) == true
          self << item
        else
          self.input(item)
        end
      end
    elsif data.kind_of?(Numeric)
      self << data
    else
      begin
        raise RuntimeError
      rescue
        puts "is the data numerable?"
      end
    end
  end
end

## need to extend the Array class in order to perform basic math. Otherwise,
#  the methods tend to crash as they attempt to run on Array instances.

class Array

  def sum
    self.inject(0) do |a,x|
      a + x
    end
  end

  def average
    self.sum.to_f / self.size
  end

  def median
    case self.size % 2
      when 0 then self.sort[self.size/2-1,2].average
      when 1 then self.sort[self.size/2].to_f
    end if self.size > 0
  end

end

#########################

describe DataSet do

  it "inherits from Array" do
    DataSet.kind_of?(Array) == true
  end

  it "returns 0 for an empty array" do
    DataSet.new.sum.should eq 0
  end

  it "finds the total value of its data" do
    data = DataSet.new
    data << 1
    data << 2
    data.sum.should eq 3
  end

  it "inputs data one at a time or in batches" do
    example1 = DataSet.new.input(1)
    example1.first.should eq 1
    
    example2 = DataSet.new.input([1,2,3])
    example2.last.should eq 3

    example3 = DataSet.new.input((4..6))
    example3.last.should eq 6

    example4 = DataSet.new.input(1.3)
    example4.last.should be_a_kind_of Float
  end

  it "takes numerical data only" do
    data = "cat"
    DataSet.new.input("cat").should raise_error
  end

  it "knows its average value" do
    example = DataSet.new
    example.input(1..100)
    example.average.should eq 50.5
  end

  it "knows its median (aka middle) value" do
    example = DataSet.new
    example.input(1..100)
    example.median.should eq 50.5
  end

end