Without code change, new test gives error below.

Failure/Error: @cache[:x].should be_nil
     ArgumentError:
       comparison of Time with nil failed
     # ./lib/volatile_hash.rb:49:in `>'
     # ./lib/volatile_hash.rb:49:in `expired?'
     # ./lib/volatile_hash.rb:18:in `[]'
Merge pull request #3 from nathanl/repeated_expired_access

Without code change, new test gives error below.