Ruby

test_string.rb,test_symbol.rb: add some tests

• test/ruby/test_string.rb: add more test cases for String#casecmp.
• test/ruby/test_symbol.rb: ditto for Symbol#{casecmp,casecmp?}.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58836 b2dd03c8-39d4-4d8f-98ff-823fe69b080e