decouples the implementation of the inflector from its test suite

Trying alternative implementations of the inflections
is hard because the suite is coupled with the current
one, setting ivars by hand etc. This commit relies on
initialize_dup, as long as you maintain that one you
can tweak the implementation.

activesupport/lib/active_support/inflector/inflections.rb

@@ -28,6 +28,13 @@ def initialize
         @plurals, @singulars, @uncountables, @humans, @acronyms, @acronym_regex = [], [], [], [], {}, /(?=a)b/
       end
 
+      # Private, for the test suite.
+      def initialize_dup(orig)
+        %w(plurals singulars uncountables humans acronyms acronym_regex).each do |scope|
+          instance_variable_set("@#{scope}", orig.send(scope).dup)
+        end
+      end
+
       # Specifies a new acronym. An acronym must be specified as it will appear in a camelized string.  An underscore
       # string that contains the acronym will retain the acronym when passed to `camelize`, `humanize`, or `titleize`.
       # A camelized string that contains the acronym will maintain the acronym when titleized or humanized, and will

activesupport/test/inflector_test.rb

@@ -26,11 +26,10 @@ def test_pluralize_empty_string
   end
 
   def test_uncountable_word_is_not_greedy
+    with_dup do
       uncountable_word = "ors"
       countable_word = "sponsor"
 
-    cached_uncountables = ActiveSupport::Inflector.inflections.uncountables
-
       ActiveSupport::Inflector.inflections.uncountable << uncountable_word
 
       assert_equal uncountable_word, ActiveSupport::Inflector.singularize(uncountable_word)
@@ -40,9 +39,7 @@ def test_uncountable_word_is_not_greedy
       assert_equal "sponsor", ActiveSupport::Inflector.singularize(countable_word)
       assert_equal "sponsors", ActiveSupport::Inflector.pluralize(countable_word)
       assert_equal "sponsor", ActiveSupport::Inflector.singularize(ActiveSupport::Inflector.pluralize(countable_word))
-
-  ensure
-    ActiveSupport::Inflector.inflections.instance_variable_set :@uncountables, cached_uncountables
+    end
   end
 
   SingularToPlural.each do |singular, plural|
@@ -349,16 +346,16 @@ def test_symbol_to_lower_camel
   %w{plurals singulars uncountables humans}.each do |inflection_type|
     class_eval <<-RUBY, __FILE__, __LINE__ + 1
       def test_clear_#{inflection_type}
-        cached_values = ActiveSupport::Inflector.inflections.#{inflection_type}
+        with_dup do
           ActiveSupport::Inflector.inflections.clear :#{inflection_type}
           assert ActiveSupport::Inflector.inflections.#{inflection_type}.empty?, \"#{inflection_type} inflections should be empty after clear :#{inflection_type}\"
-        ActiveSupport::Inflector.inflections.instance_variable_set :@#{inflection_type}, cached_values
+        end
       end
     RUBY
   end
 
   def test_clear_all
-    cached_values = ActiveSupport::Inflector.inflections.plurals.dup, ActiveSupport::Inflector.inflections.singulars.dup, ActiveSupport::Inflector.inflections.uncountables.dup, ActiveSupport::Inflector.inflections.humans.dup
+    with_dup do
       ActiveSupport::Inflector.inflections do |inflect|
         # ensure any data is present
         inflect.plural(/(quiz)$/i, '\1zes')
@@ -373,14 +370,11 @@ def test_clear_all
         assert inflect.uncountables.empty?
         assert inflect.humans.empty?
       end
-    ActiveSupport::Inflector.inflections.instance_variable_set :@plurals, cached_values[0]
-    ActiveSupport::Inflector.inflections.instance_variable_set :@singulars, cached_values[1]
-    ActiveSupport::Inflector.inflections.instance_variable_set :@uncountables, cached_values[2]
-    ActiveSupport::Inflector.inflections.instance_variable_set :@humans, cached_values[3]
+    end
   end
 
   def test_clear_with_default
-    cached_values = ActiveSupport::Inflector.inflections.plurals.dup, ActiveSupport::Inflector.inflections.singulars.dup, ActiveSupport::Inflector.inflections.uncountables.dup, ActiveSupport::Inflector.inflections.humans.dup
+    with_dup do
       ActiveSupport::Inflector.inflections do |inflect|
         # ensure any data is present
         inflect.plural(/(quiz)$/i, '\1zes')
@@ -395,10 +389,7 @@ def test_clear_with_default
         assert inflect.uncountables.empty?
         assert inflect.humans.empty?
       end
-    ActiveSupport::Inflector.inflections.instance_variable_set :@plurals, cached_values[0]
-    ActiveSupport::Inflector.inflections.instance_variable_set :@singulars, cached_values[1]
-    ActiveSupport::Inflector.inflections.instance_variable_set :@uncountables, cached_values[2]
-    ActiveSupport::Inflector.inflections.instance_variable_set :@humans, cached_values[3]
+    end
   end
 
   Irregularities.each do |irregularity|
@@ -447,26 +438,28 @@ def test_clear_with_default
     end
   end
 
-  { :singulars => :singular, :plurals => :plural, :uncountables => :uncountable, :humans => :human }.each do |scope, method|
+  %w(plurals singulars uncountables humans acronyms).each do |scope|
     ActiveSupport::Inflector.inflections do |inflect|
       define_method("test_clear_inflections_with_#{scope}") do
-        # save the inflections
-        values = inflect.send(scope)
-
+        with_dup do
           # clear the inflections
           inflect.clear(scope)
-
           assert_equal [], inflect.send(scope)
-
-        # restore the inflections
-        if scope == :uncountables
-          inflect.send(method, values)
-        else
-          values.reverse.each { |value| inflect.send(method, *value) }
         end
-
-        assert_equal values, inflect.send(scope)
       end
     end
   end
+
+  # Dups the singleton and yields, restoring the original inflections later.
+  # Use this in tests what modify the state of the singleton.
+  #
+  # This helper is implemented by setting @__instance__ because in some tests
+  # there are module functions that access ActiveSupport::Inflector.inflections,
+  # so we need to replace the singleton itself.
+  def with_dup
+    original = ActiveSupport::Inflector.inflections
+    ActiveSupport::Inflector::Inflections.instance_variable_set(:@__instance__, original.dup)
+  ensure
+    ActiveSupport::Inflector::Inflections.instance_variable_set(:@__instance__, original)
+  end
 end