Add RubyVM tests

These tests the number of global contants before and after running
minitest. They showed that integration tests were creating a global
constant which is expensive. That global constant is in `url_helpers`
and the fix has been merged into master Rails.

Author: eileencodes

test/controllers/documents_rubyvm_index_test.rb

@@ -0,0 +1,15 @@
+require 'test_helper'
+
+class DocumentsControllerTest < ActionController::TestCase
+  test "index" do
+    get :index
+    assert_equal 200, response.status
+  end
+end
+
+Minitest.run_one_method(DocumentsControllerTest, 'test_index')
+
+# ruby -Ilib:test test/controllers/documents_rubyvm_index_test.rb
+puts RubyVM.stat
+Minitest.run_one_method(DocumentsControllerTest, 'test_index')
+puts RubyVM.stat

test/integration/documents_rubyvm_index_test.rb

@@ -0,0 +1,16 @@
+require 'test_helper'
+ActiveSupport::Dependencies.constantize('DocumentsController')
+
+class DocumentsIntegrationTest < ActionDispatch::IntegrationTest
+  test "index" do
+    get '/documents'
+    assert_equal 200, response.status
+  end
+end
+
+Minitest.run_one_method(DocumentsIntegrationTest, 'test_index')
+
+# ruby -Ilib:test test/integration/documents_rubyvm_index_test.rb
+puts RubyVM.stat
+Minitest.run_one_method(DocumentsIntegrationTest, 'test_index')
+puts RubyVM.stat