Add spec for main.ruby2_keywords

Author: eregon

core/main/ruby2_keywords_spec.rb

@@ -0,0 +1,11 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+ruby_version_is "2.7" do
+  describe "main.ruby2_keywords" do
+    it "is the same as Object.ruby2_keywords" do
+      main = TOPLEVEL_BINDING.receiver
+      main.should have_private_method(:ruby2_keywords)
+    end
+  end
+end