ruby_flatten_recursive.rb

# Ruby Version: 2.3.1p112
# Author: Vlad Covaliov
# Date: 06.09.2016

require 'test/unit'

module ArrayUtils
  # Flatten nested array using a recursive method. Non-Destructive Method
  # 
  # @param [Array, #read] content we want to flatten
  # @return [Array] a new flat object with the contents
  def recursive_flatten(object)
    raise RuntimeError, "#{object.inspect} not convertible to array" unless object.respond_to?(:to_a)
    result = []

    object.to_a.each do |elem|
      if elem.kind_of?(Array)
        result.push(*recursive_flatten(elem))
      else
        result.push(elem)
      end
    end
    result
  end
end

class TestArrayUtils < Test::Unit::TestCase
  include ArrayUtils

  def test_recursive_flatten
    # Negative test with wrong object type
    assert_raise RuntimeError do
      recursive_flatten("test")
    end
    # Negative test for nil 
    assert_equal([], recursive_flatten(nil))

    # Empty Array
    assert_equal([], recursive_flatten([]))
    # 1-level array
    assert_equal([1,2,3], recursive_flatten([1,2,3]))
    # 2-level array
    assert_equal([1,2,3], recursive_flatten([[1],[2],[3]]))
    # multi-level array
    assert_equal([1,2,3,4,5,6], recursive_flatten([[1,2,[3]],[4,5],[[[6]]]]))
  end
end

# Loaded suite ruby_flatten
# Started
# .

# Finished in 0.000457007 seconds.
# -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
# 1 tests, 6 assertions, 0 failures, 0 errors, 0 pendings, 0 omissions, 0 notifications
# 100% passed
# -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
# 2188.15 tests/s, 13128.90 assertions/s