assert_template fails with empty string when a template has been rendered

For instance, it prevents false positive in this case:

    file = nil
    get :index
    assert_template("#{file}")

actionpack/CHANGELOG.md

@@ -1,5 +1,9 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   `assert_template` is no more passing with empty string when some template has been rendered.
+
+    *Roberto Soares*
+
 *   Allow setting a symbol as path in scope on routes. This is now allowed:
 
         scope :api do

actionpack/lib/action_controller/test_case.rb

@@ -94,10 +94,14 @@ def assert_template(options = {}, message = nil)
         matches_template =
           case options
           when String
-            rendered.any? do |t, num|
-              options_splited = options.split(File::SEPARATOR)
-              t_splited = t.split(File::SEPARATOR)
-              t_splited.last(options_splited.size) == options_splited
+            if options.empty?
+              rendered.blank?
+            else
+              rendered.any? do |t, num|
+                options_splited = options.split(File::SEPARATOR)
+                t_splited = t.split(File::SEPARATOR)
+                t_splited.last(options_splited.size) == options_splited
+              end
             end
           when Regexp
             rendered.any? { |t,num| t.match(options) }

actionpack/test/controller/action_pack_assertions_test.rb

@@ -447,6 +447,13 @@ def test_with_nil_fails_when_template_rendered
     end
   end
 
+  def test_with_empty_string_fails_when_template_rendered
+    get :hello_world
+    assert_raise(ActiveSupport::TestCase::Assertion) do
+      assert_template ""
+    end
+  end
+
   def test_passes_with_correct_string
     get :hello_world
     assert_template 'hello_world'