Reverse String

reverse_string.rb

require 'minitest/autorun'

# Implementation of my_reverse method
# This method takes a string as input and returns the string in reverse order.
# The method also handles edge cases such as empty strings and single-character strings.
# The method uses a loop to iterate through the string in reverse order and constructs the reversed string.


# Custom error class for handling invalid input types
# This class inherits from StandardError and provides a custom error message.
# It is raised when the input to the my_reverse method is not a string.
class ReverseDataTypeError < StandardError
  def message
    'Input must be a string'
  end
end


# my_reverse method implementation
def my_reverse(string)
  # check if string is empty or actually a string or string is nil
  raise ReverseDataTypeError unless string.is_a?(String)
  return '' if string.empty?
  # check if string is a single character
  return string if string.length == 1

  reversed_string = ''

  string.length.times do |i|
    reversed_string += string[string.length - 1 - i]
  end
  reversed_string

rescue ReverseDataTypeError => e
  puts "Error: #{e.message}\n"
  ''
end

# test cases without minitest
puts my_reverse('') # ''
puts my_reverse('a') # 'a'
puts my_reverse('ab') # 'ba'
puts my_reverse('abc') # 'cba'
puts my_reverse('abcd') # 'dcba'
puts my_reverse(123456) # ''
puts my_reverse('ab' * 1000) # 'ba' * 1000
puts my_reverse(nil) # ''


# test cases with minitest
class TestMyReverse < Minitest::Test
  def test_empty_string
    assert_equal '', my_reverse('')
  end

  def test_single_character
    assert_equal 'a', my_reverse('a')
  end

  def test_two_characters
    assert_equal 'ba', my_reverse('ab')
  end

  def test_three_characters
    assert_equal 'cba', my_reverse('abc')
  end

  def test_four_characters
    assert_equal 'dcba', my_reverse('abcd')
  end

  def test_integer_input
    assert_equal '', my_reverse(123456)
  end

  def test_nil_input
    assert_equal '', my_reverse(nil)
  end

  def test_large_string
    assert_equal 'ba' * 1000, my_reverse('ab' * 1000)
  end
end