diff --git a/activesupport/test/caching_test.rb b/activesupport/test/caching_test.rb
index d55cc5d3b0..8287e62f4c 100644
--- a/activesupport/test/caching_test.rb
+++ b/activesupport/test/caching_test.rb
@@ -60,36 +60,25 @@ class CacheKeyTest < ActiveSupport::TestCase
   end
 
   def test_expand_cache_key_with_rails_cache_id
-    begin
-      ENV['RAILS_CACHE_ID'] = 'c99'
+    with_env('RAILS_CACHE_ID' => 'c99') do
       assert_equal 'c99/foo', ActiveSupport::Cache.expand_cache_key(:foo)
       assert_equal 'c99/foo', ActiveSupport::Cache.expand_cache_key([:foo])
       assert_equal 'c99/foo/bar', ActiveSupport::Cache.expand_cache_key([:foo, :bar])
       assert_equal 'nm/c99/foo', ActiveSupport::Cache.expand_cache_key(:foo, :nm)
       assert_equal 'nm/c99/foo', ActiveSupport::Cache.expand_cache_key([:foo], :nm)
       assert_equal 'nm/c99/foo/bar', ActiveSupport::Cache.expand_cache_key([:foo, :bar], :nm)
-    ensure
-      ENV['RAILS_CACHE_ID'] = nil
     end
   end
 
   def test_expand_cache_key_with_rails_app_version
-    begin
-      ENV['RAILS_APP_VERSION'] = 'rails3'
+    with_env('RAILS_APP_VERSION' => 'rails3') do
       assert_equal 'rails3/foo', ActiveSupport::Cache.expand_cache_key(:foo)
-    ensure
-      ENV['RAILS_APP_VERSION'] = nil
     end
   end
 
   def test_expand_cache_key_rails_cache_id_should_win_over_rails_app_version
-    begin
-      ENV['RAILS_CACHE_ID'] = 'c99'
-      ENV['RAILS_APP_VERSION'] = 'rails3'
+    with_env('RAILS_CACHE_ID' => 'c99', 'RAILS_APP_VERSION' => 'rails3') do
       assert_equal 'c99/foo', ActiveSupport::Cache.expand_cache_key(:foo)
-    ensure
-      ENV['RAILS_CACHE_ID'] = nil
-      ENV['RAILS_APP_VERSION'] = nil
     end
   end
 
@@ -124,6 +113,16 @@ class CacheKeyTest < ActiveSupport::TestCase
   def test_expand_cache_key_of_array_like_object
     assert_equal 'foo/bar/baz', ActiveSupport::Cache.expand_cache_key(%w{foo bar baz}.to_enum)
   end
+
+  private
+
+  def with_env(kv)
+    old_values = {}
+    kv.each { |key, value| old_values[key], ENV[key] = ENV[key], value }
+    yield
+  ensure
+    old_values.each { |key, value| ENV[key] = value}
+  end
 end
 
 class CacheStoreSettingTest < ActiveSupport::TestCase