It appears that the test coverage provided by the oqgraph MTR suite is not sufficient. Since it was not possible to obtain gcov numbers, the observations below are based on a visual examination of the test suite.

It appears that the following is missing from the test suite:

• a complete list of the SELECT statements that are accepted by the engine, as described in
  the manual, including those with latch=0 or latch = NULL;
• DML and SELECT statements with weight != 0
• queries that will be rejected by the storage engine, including invalid DDL/ALTER, DML that modifies non-modifiable columns, CREATE TABLE with an invalid layout, etc.
• an enumeration of the DML/DDL/ALTER statements that are accepted by the engine, so that all the engine capabilities the handler advertises and all the API calls are exercised, including ALTER ENGINE=, INSERT ... SELECT, CREATE .. SELECT etc.
• verification of each statement after it is executed, e.g. a SELECT must be done after TRUNCATE for a proper test for truncation; an I_S query and CREATE, etc. must be performed after TRUNCATE to test that the table is truly gone, etc.;
• a dataset that is sized appropriately for MTR execution (10K nodes?). Either in the form of INSERT statements or a stored procedure, plus some SELECT queries on top of that dataset;
• joins and other cross-engine operations;