The test name is misleading. It says

test_should_cache_with_trailing_slash_on_url

A trailing slash is removed when a page is cached.

What the test meant to say was : a url with trailing slash
should be cached and the cached page should not have any
trailing slash.

This patch clarifies the name a bit.

actionpack/test/controller/caching_test.rb

@@ -127,7 +127,7 @@ def test_should_obey_http_accept_attribute
     assert_equal 'I am xml', @response.body
   end
 
-  def test_should_cache_with_trailing_slash_on_url
+  def test_cached_page_should_not_have_trailing_slash_even_if_url_has_trailing_slash
     @controller.class.cache_page 'cached content', '/page_caching_test/trailing_slash/'
     assert File.exist?("#{FILE_STORE_PATH}/page_caching_test/trailing_slash.html")
   end