Usage

The make task `update-coverage' retrieves simplecov for coverage report.

COVERAGE=1 make test-all TESTS=test/cgi

it generates test coverage to coverage directory.

Limitation

 * test_coverage.rb and test_process.rb broke test suit with SimpleCov
 * some tests failed randomly.

TODO

 * more reduce bundled simplecov(additional configuration, formatter, etc)
 * measure rubyspec coverage
