diff --git a/lib/omniauth/strategy.rb b/lib/omniauth/strategy.rb
index fcd8e65..88aebc8 100644
--- a/lib/omniauth/strategy.rb
+++ b/lib/omniauth/strategy.rb
@@ -237,9 +237,6 @@ module OmniAuth
 
     def mock_request_call
       setup_phase
-      if response = call_through_to_app
-        return response
-      end
 
       if request.params['origin']
         @env['rack.session']['omniauth.origin'] = request.params['origin']
@@ -356,14 +353,6 @@ module OmniAuth
       request.query_string.empty? ? "" : "?#{request.query_string}"
     end
 
-    def call_through_to_app
-      status, headers, body = *call_app!
-      session['query_params'] = Rack::Request.new(env).params
-      @response = Rack::Response.new(body, status, headers)
-
-      status == 404 ? nil : @response.finish
-    end
-
     def call_app!(env = @env)
       @app.call(env)
     end
diff --git a/spec/omniauth/strategy_spec.rb b/spec/omniauth/strategy_spec.rb
index 01f10bc..41e71fa 100644
--- a/spec/omniauth/strategy_spec.rb
+++ b/spec/omniauth/strategy_spec.rb
@@ -477,6 +477,11 @@ describe OmniAuth::Strategy do
     end
 
     context 'test mode' do
+      let(:app) do
+        # In test mode, the underlying app shouldn't be called on request phase.
+        lambda { |env| [404, {"Content-Type" => "text/html"}, []] }
+      end
+
       before do
         OmniAuth.config.test_mode = true
       end