Tests for the implementation of the 'The Fast Fourier Transform Algorithm'

fft.spec.rb

require 'minitest/autorun'
require './fft'

describe FFT do

  before do
    @fft = FFT.new
  end

  describe "#fft" do
    it "should return a point-wise representation of a polynomial of degree 1" do
      assert_equal(@fft.fft([1, 1]), [
        Complex(2, +0),
        Complex(0.0, -1.2246467991473532e-16)
      ])
    end

    it "should return a point-wise representation of a polynomial of degree 3" do
      assert_equal(@fft.fft([1, 1, 0, 0]), [
        Complex(2, +0),
        Complex(1.0, -1.0),
        Complex(0.0, -1.2246467991473532e-16),
        Complex(0.9999999999999998, +1.0)
      ])
    end

    it "should return a point-wise representation of a polynomial of degree 7" do
      assert_equal(@fft.fft([1, 1, 1, 1, 0, 0, 0, 0]), [
        Complex(4, +0),
        Complex(1.0, -2.414213562373095),
        Complex(-1.2246467991473532e-16, -1.2246467991473532e-16),
        Complex(1.0, -0.4142135623730949),
        Complex(0.0, -2.4492935982947064e-16),
        Complex(0.9999999999999998, +0.41421356237309515),
        Complex(1.2246467991473532e-16, -1.224646799147353e-16),
        Complex(0.9999999999999994, +2.414213562373095)
      ])
    end
  end
end

Full blog post can be found here: https://medium.com/@diegocasmo/the-fast-fourier-transform-algorithm-6f06900c565b#.lqtcu69lk