A simple re-implementation of Array#flatten. Run tests with rspec

my_flatten.rb

class Array

  # Get a one-dimensional array by combining elements of nested arrays.
  # 
  # ==== Examples
  #
  #   [[3, 4], 5, [[6, 7, 8], 9]] #=> [3, 4, 5, 6, 7, 8, 9]
  # 
  def my_flatten
    result = []
    self.each do |elem|
      if elem.is_a?(Array)
        result += elem.my_flatten
      else
        result << elem
      end
    end
    result
  end
end


describe "Array#my_flatten" do
  it "is a no-op on an already flat array" do
    expect([].my_flatten).to eq([])
    expect([50].my_flatten).to eq([50])
    expect([3, 4, 9].my_flatten).to eq([3, 4, 9])
  end

  it "always returns a new array" do
    arr = []
    expect(arr.my_flatten).not_to equal(arr.my_flatten)
  end

  it "flattens many levels of nesting" do
    arr_1 = [[3], 4, 5, [[6, 7], 8], 9, 10]
    expect(arr_1.my_flatten).to eq([3, 4, 5, 6, 7, 8, 9, 10])

    arr_2 = [[[[[[[[[[10]]]]], 11, [[[[[[[[[[[[[[[[[12]]]]]]]]]]]]]]]]]]]]]]
    expect(arr_2.my_flatten).to eq([10, 11, 12])
  end

  it "ignores empty arrays" do
    arr = [3, [], 4, [[]], 5, [[], [], []], 6]
    expect(arr.my_flatten).to eq([3, 4, 5, 6])
  end
end