add deprecation warning to assert_nothing_raised and changelog entry

activesupport/CHANGELOG.md

+*   Deprecate arguments on `assert_nothing_raised`.
+
+    `assert_nothing_raised` does not assert the arguments that have been passed
+    in (usually a specific exception class) since the method only yields the
+    block. So as not to confuse the users that the arguments have meaning, they
+    are being deprecated.
+
+    *Tara Scherner de la Fuente*
+
 *   Make `benchmark('something', silence: true)` actually work
 
     *DHH*

activesupport/lib/active_support/test_case.rb

@@ -74,7 +74,11 @@ def test_order
     #   assert_nothing_raised do
     #     perform_service(param: 'no_exception')
     #   end
-    def assert_nothing_raised
+    def assert_nothing_raised(*args)
+      if args.present?
+      ActiveSupport::Deprecation.warn("Passing arguments to assert_nothing_raised
+        is deprecated and will be removed in Rails 5.1.")
+      end
       yield
     end
   end