Reset rack.input when the environment is scrubbed for the next request

Before this change, posted parameters would leak across requests. The included
test case failed like so:

      1) Failure:
    TestCaseTest#test_multiple_mixed_method_process_should_scrub_rack_input:
    --- expected
    +++ actual
    @@ -1 +1 @@
    -{"bar"=>"an bar", "controller"=>"test_case_test/test", "action"=>"test_params"}
    +{"foo"=>"an foo", "bar"=>"an bar", "controller"=>"test_case_test/test", "action"=>"test_params"}

An argument could be made that this situation isn't encountered often and that
one should limit the number of requests per test case, but I still think the
parameter leaking is an unexpected side-effect.

2 files changed, 9 insertions, 0 deletions

diff --git a/actionpack/lib/action_controller/test_case.rb b/actionpack/lib/action_controller/test_case.rb
index b1b3e87934..6c5d7b5e37 100644
--- a/actionpack/lib/action_controller/test_case.rb
+++ b/actionpack/lib/action_controller/test_case.rb
@@ -620,6 +620,7 @@ module ActionController
         env.delete_if { |k, v| k =~ /^action_dispatch\.rescue/ }
         env.delete 'action_dispatch.request.query_parameters'
         env.delete 'action_dispatch.request.request_parameters'
+        env['rack.input'] = StringIO.new
         env
       end
 
diff --git a/actionpack/test/controller/test_case_test.rb b/actionpack/test/controller/test_case_test.rb
index ea59156f65..e288b51716 100644
--- a/actionpack/test/controller/test_case_test.rb
+++ b/actionpack/test/controller/test_case_test.rb
@@ -854,6 +854,14 @@ XML
     assert_nil cookies['foo']
   end
 
+  def test_multiple_mixed_method_process_should_scrub_rack_input
+    post :test_params, params: { id: 1, foo: 'an foo' }
+    assert_equal({"id"=>"1", "foo" => "an foo", "controller"=>"test_case_test/test", "action"=>"test_params"}, ::JSON.parse(@response.body))
+
+    get :test_params, params: { bar: 'an bar' }
+    assert_equal({"bar"=>"an bar", "controller"=>"test_case_test/test", "action"=>"test_params"}, ::JSON.parse(@response.body))
+  end
+
   %w(controller response request).each do |variable|
     %w(get post put delete head process).each do |method|
       define_method("test_#{variable}_missing_for_#{method}_raises_error") do