How to detect classes not having the unit tests.

Only part of class files have the equivalent test files In BioRuby.
In order to see a whole coverage of the unit test to the all class files with rcov, I have to develop the empty test files for the class files not having them.
The process is as follows.

First, make sure which files in the lib directory don't have the equivalent test files

Seconde, prepare each test file in witch the equivalent lib file is required.

Third, execute rcov to visualize the whole coverage