The MySQL tests for TokuDB are divided into common tests and tests specific to a
particular MySQL distribution.

The tests that are common for all MySQL distributions can be found in the
svn:tokudb/mysql/tests/mysql-test directory.

The tests that are specific to a particular distribution can be found in that
distribution's mysql-test directory.  For example, tests that are specific to
MySQL 5.5.21 are found in the svn:tokudb/mysql.com/mysql-5.5.21/mysql-test directory.

When we run tests on a particular MySQL distribution, we run the union of the common
tests and the tests that are in that distributions mysql-test directory.  The union
is formed by overlaying the common tests with the distribution specific tests.  

Here is an example.  There are a bunch of alter table tests in that should be common
to all MySQL distributions.  These tests are in the 
svn:tokudb/mysql/tests/mysql-test/suite/tokudb.alter_table directory.
However, the ai_di.test has behaviour that is different on MySQL 5.5 than previous 
MySQL distributions.  There is another version of this test in the MySQL 5.5.21 source
directory.  This version replaces the common test since it has the same test name.

It is easy to disable a test.  Just add the test name to the "disabled.def" file in the
test directory.

We use the run.mysql.tests.bash script from the mysql/scripts directory to run the tests.

