Flatten Array of Integers Without Using Flatten

flatten_array_without_flatten.rb

def flatten_array(input)
  input.to_s.gsub(/\[|,|\]/, ' ').split.map(&:to_i)
end

# TEST 1
input    = [[1, 2, [3]], 4]
expected = [1, 2, 3, 4]
actual   = flatten_array(input)

puts
puts "Input:    #{input}"
puts "Expected: #{expected}"
puts "Actual:   #{actual}"
puts

if expected == actual
  puts 'Test passes'
else
  puts 'Test fails'
end


# TEST 2
input    = [[[22, [[333]]], 88, [12, 99], [[123]], [5]]]
expected =  [22, 333, 88, 12, 99, 123, 5]
actual   = flatten_array(input)

puts
puts "Input:    #{input}"
puts "Expected: #{expected}"
puts "Actual:   #{actual}"
puts

if expected == actual
  puts 'Test passes'
else
  puts 'Test fails'
end

puts