Merge session arg with existing session instead of overwriting

This may break existing tests that are asserting the whole session contents
but should not break existing tests that are asserting individual keys - e.g:

class SomeControllerTest < ActionController::TestCase
  setup do
    session['user_id'] = 1
  end

  test "some test" do
    get :some_action, nil, { 'another_var' => 2 }

    # This assertion will now fail
    assert_equal({ 'another_var' => 2 }, session)

    # This assertion will still pass
    assert_equal 2, session['another_var]
  end
end

Fixes #1529.

1 files changed, 20 insertions, 0 deletions

diff --git a/actionpack/test/controller/test_case_test.rb b/actionpack/test/controller/test_case_test.rb
index e8411bae0c..03b7396d5b 100644
--- a/actionpack/test/controller/test_case_test.rb
+++ b/actionpack/test/controller/test_case_test.rb
@@ -224,6 +224,26 @@ XML
     assert_equal 'value2', session[:symbol]
   end
 
+  def test_process_merges_session_arg
+    session[:foo] = 'bar'
+    get :no_op, nil, { :bar => 'baz' }
+    assert_equal 'bar', session[:foo]
+    assert_equal 'baz', session[:bar]
+  end
+
+  def test_merged_session_arg_is_retained_across_requests
+    get :no_op, nil, { :foo => 'bar' }
+    assert_equal 'bar', session[:foo]
+    get :no_op
+    assert_equal 'bar', session[:foo]
+  end
+
+  def test_process_overwrites_existing_session_arg
+    session[:foo] = 'bar'
+    get :no_op, nil, { :foo => 'baz' }
+    assert_equal 'baz', session[:foo]
+  end
+
   def test_session_is_cleared_from_controller_after_reset_session
     process :set_session
     process :reset_the_session