koans/about_to_str.rb

   1 require File.expand_path(File.dirname(__FILE__) + '/edgecase')
   2
   3 class AboutToStr < EdgeCase::Koan
   4
   5   class CanNotBeTreatedAsString
   6     def to_s
   7       "non-string-like"
   8     end
   9   end
  10
  11   def test_to_s_returns_a_string_representation
  12     not_like_a_string = CanNotBeTreatedAsString.new
  13     assert_equal __, not_like_a_string.to_s
  14   end
  15
  16   def test_normally_objects_cannot_be_used_where_strings_are_expected
  17     assert_raise(___) do
  18       File.exist?(CanNotBeTreatedAsString.new)
  19     end
  20   end
  21
  22   # ------------------------------------------------------------------
  23
  24   class CanBeTreatedAsString
  25     def to_s
  26       "string-like"
  27     end
  28
  29     def to_str
  30       to_s
  31     end
  32   end
  33
  34   def test_to_str_also_returns_a_string_representation
  35     like_a_string = CanBeTreatedAsString.new
  36     assert_equal __, like_a_string.to_str
  37   end
  38
  39   def test_to_str_allows_objects_to_be_treated_as_strings
  40     assert_equal __, File.exist?(CanBeTreatedAsString.new)
  41   end
  42
  43   # ------------------------------------------------------------------
  44
  45   def acts_like_a_string?(string)
  46     string = string.to_str if string.respond_to?(:to_str)
  47     string.is_a?(String)
  48   end
  49
  50   def test_user_defined_code_can_check_for_to_str
  51     assert_equal __, acts_like_a_string?(CanNotBeTreatedAsString.new)
  52     assert_equal __,  acts_like_a_string?(CanBeTreatedAsString.new)
  53   end
  54 end