fix a typo [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48343 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Fix typos in assert messages [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48344 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
fix a typo in comment [ci skip]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48345 b2dd03c8-39d4-4d8f-98ff-823fe69b080e