test with psych

* test/rubygems/test_gem_specification.rb (test_to_yaml_emits_syck_compat_yaml):
  test with psych.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@35442 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/rubygems/test_gem_specification.rb

@@ -1210,13 +1210,16 @@ end
 
   def test_to_yaml_emits_syck_compat_yaml
     if YAML.const_defined?(:ENGINE) && !YAML::ENGINE.syck?
+      yamler, YAML::ENGINE.yamler = YAML::ENGINE.yamler, 'psych'
+    end
+    begin
       @a1.add_dependency "gx", "1.0.0"
 
       y = @a1.to_yaml
 
       refute_match %r!^\s*- - =!, y
-    else
-      skip "Only validates psych yaml"
+    ensure
+      YAML::ENGINE.yamler = yamler if yamler
     end
   end