Array flattener

array_flattener.rb

#!/usr/bin/env ruby

require 'minitest'

class ArrayFlattener
  def perform(nested_array)
    nested_array.inject([]) do |result, item|
      if item.is_a?(Array)
        result.push *self.perform(item)
      else
        result << item
      end
    end
  end
end

class ArrayFlattenerTest < MiniTest::Test
  def test_regular_array
    flattener = ArrayFlattener.new
    assert_equal [1,2,3,4], flattener.perform([1,2,3,4])
  end
  def test_empty_array
    flattener = ArrayFlattener.new
    assert_equal [], flattener.perform([])
  end
  def test_nested_array
    flattener = ArrayFlattener.new
    assert_equal [1,2,3,4], flattener.perform([1,2,[3],4])
  end
  def test_deep_nested_array
    flattener = ArrayFlattener.new
    assert_equal [1,2,3,4], flattener.perform([1,[[2,[3]],4]])
  end
  def test_ignore_empty_array
    flattener = ArrayFlattener.new
    assert_equal [1,3,4], flattener.perform([1,[],[3],4])
  end
end

MiniTest.run