To be able to see the level of coverage with the current test suite,
do the following:

  - Make sure gcov is installed
  - Compile the MySQL distribution with BUILD/compile-pentium64-gcov (if your
    machine does not have a pentium CPU, hack this script, or just live with
	the pentium-specific stuff)
  - In the mysql-test directory, run this command: ./mysql-test-run -gcov
  - To see the level of coverage for a given source file:
     grep -1 source_file_name ../mysql-test-gcov.msg
  - To see which lines are not yet covered, look at source_file_name.gcov in
    the source tree.  You can find this by doing something like:
    find source-directory -name "mysqld.cc.gcov"
    Then think hard about a test case that will cover those lines, and write
    one!