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The basics

At the core, it is very simple. The client program mysqltest executes a test file and compares the produced output with the result file. If they match, the test is passed, otherwise it is failed. Tthis approach can be used to test any SQL statements, as well as other executables (with the exec command).

The complete process of testing is governed and monitored by a driver script or mtr for short (for convenience, mtr is created as a symbolic link to It is responsible for preparing the test environment, creating a list of all tests to run, running them, and producing the report at the end. It can run many tests in parallel, execute tests in the order that minimizes server restarts (as they are slow), run tests in a debugger or under valgrind or strace, and so on.

Test files are located in suites. A suite is a directory that contains test files, result files, and optional configuration files. The mtr loos for suites in the mysql-test/suite directory, and in the mysql-test subdirectories of plugins and storage engine directories. For example, these are valid suite paths:

  • mysql-test/suite/rpl
  • mysql-test/suite/handler
  • storage/example/mysql-test/demo
  • plugin/auth_pam/mysql-test/pam

In all cases, suite directory name is the suite name. A notable historical exception is the main suite, which is located directly in the mysql-test

Test files have .test extension and can be placed directly in the suite directory (for example, mysql-test/suite/handler/interface.test) or in the t subdirectory (like mysql-test/suite/rpl/t/rpl_alter.test or mysql-test/t/grant.test). Similarly, result files have .result extenstion and can be in the suite directory too, or in the r subdirectory.

A test file can include other files (with the source command). These include files can have any name and be placed anywhere, but customarily they have .inc extension and located in the suite directory or in the inc or include subdirectory (for example, mysql-test/suite/handler/ or mysql-test/include/

Other files that affect testing, while not being tests themselves, are:

  • disabled.def
  • suite.opt
  • other *.opt files
  • my.cnf
  • other *.cnf files
  • combinations
  • other *.combinations files
  • *.sh files
  • *.require files
  • *.rdiff files
  • valgrind.supp

See Auxiliary files for details.


In addition to regular suite directories, mtr supports overlays. An overlay is a directory with the same name as an existing suite, but located in a storage engine or plugin directory. For example, a storage/myisam/mysql-test/rpl could be a myisam overlay of the rpl suite in mysql-test/suite/rpl. And plugin/daemon_example/mysql-test/demo could be a daemon_example overlay of the demo suite in storage/example/mysql-test/demo. As a special exception, an overlay of the main suite, should be called main, as in storage/pbxt/mysql-test/main.

An overlay is like a second transparent layer in a graphics editor. It can obscure, extend, or modify the background image. Also, one can notice that an overlay is very close to a UnionFS, but implemented in perl inside mtr.

An overlay can replace almost any file in the overlayed suite, or add new files. For example, if some overlay of the main suite contains include/ file, than all tests that include it will see and use the overlayed version. Or, it can create t/create.opt file (even though the main suite does not have it), and create.test will be executed with the specified additional options.

But adding an overlay never affects how the original suite is executed. That is, mtr always executes the original suite as if no overlay was present. And then, additionally, it executes a combined "union" of the overlay and the original suite. When doing that mtr takes care to avoid reexecuting tests that are not changed in the overlay. For example, creating t/create.opt in the overlay of the main suite, will only cause create.test to be executed in the overlay. But creating suite.opt affects all tests - and it will cause all tests to be re-executed with the new options.


In certain cases it make sense to run a specific test or a group of tests several times with different server settings. It can be done using so called combinations. Combinations are groups of settings that are used alternatively. A combinations file defines these alternatives using my.cnf syntax, for example




And all tests where this combinations file applies will be run three times: once for the combination called "row", and --binlog-format=row on the server command line, once for the "stmt" combination, and once for the "mix" combination.

More than one combinations file may be applicable to a given test file. In this case, mtr will run the test for all possible combinations of combinations. A test that uses replication (three combinations as above) and innodb (two combinations - innodb and xtradb), will be run six times.

Sample output

A typical mtr output looks like this

TEST                                  WORKER RESULT   TIME (ms) or COMMENT
rpl.rpl_row_find_row_debug                [ skipped ]  Requires debug build
main-pbxt.connect                         [ skipped ]  No PBXT engine
main-pbxt.mysqlbinlog_row                 [ disabled ]  test expects a non-transactional engine
rpl.rpl_savepoint 'mix,xtradb'            w2 [ pass ]    238
rpl.rpl_stm_innodb 'innodb_plugin,row'    w1 [ skipped ]  Neither MIXED nor STATEMENT binlog format
binlog.binlog_sf 'stmt'                   w2 [ pass ]      7
unit.dbug                                 w2 [ pass ]      1
maria.small_blocksize                     w1 [ pass ]     23
sys_vars.autocommit_func3 'innodb_plugin' w1 [ pass ]      5
sys_vars.autocommit_func3 'xtradb'        w1 [ pass ]      6
main.ipv6                                 w1 [ pass ]    131

Every test is printed as "suitename.testname", and a suite name may include an overlay name (like in main-pbxt). After the test name, mtr prints combinations that were applied to this test, if any.

A similar syntax can be used on the mtr command line to specify what tests to run. While it is currently not possible to specify what combinations to use, one can specify a test name and a suite name as follows:

$ ./mtr innodbsearch for innodb test in every suite from the default list, and run all that was found.
$ ./mtr main.innodbrun the innodb test from the main suite
$ ./mtr main-pbxt.innodbrun the innodb suite from the pbxt overlay of the main suite
$ ./mtr main-.innodbrun the innodb suite from the main suite and all its overlays.

Plugin support

The mtr driver has special support for MariaDB plugins.

First, on startup it copies or symlinks all dynamically build plugins into var/plugins. This allows to have many plugins loaded at the same time. For example, one can load Federated and InnoDB engines together. Also, mtr creates environment variables for every plugin with the corresponding plugin name. For example, if InnoDB engine was built, $HA_INNODB_SO will be set to or ha_innodb.dll on Windows. And the test can safely use the corresponding environment variable on all platforms to refer to a plugin file, it will always have the correct platform dependent extension.

Second, when combining server command line options (that may come from many different sources) into one long list before starting mysqld, mtr treats --plugin-load specially. Normal server semantics is to use the latest value of any particular option on the command line. If one starts the server with, for example, --port=2000 --port=3000, the server will use the last value for the port, that is 3000. To allow different .opt files to require different plugins, mtr goes through the assembled server command line, and joins all --plugin-load options into one. Additionally it removes all emtpy --plugin-load options. For example, if some test is affected by three .opt files, that contain, respectively


and, let's assume the Example engine was not built ($HA_EXAMPLE_SO is empty). Then the server will get

instead of --plugin-load=

Third, to allow plugin sources to be simply copied into the plugin/ or storage/ directories, and still not affect existing tests (even if new plugins are statically linked into the server), mtr automatically disables all optional plugins on server startup. A plugin is optional, if it can be disabled with the corresponding --skip-XXX server command line option. Mandatory plugins, like MyISAM or MEMORY, do not have --skip-XXX options (like, there is no --skip-myisam option). This mtr behavior means that no plugin, statically or dynamically built, has any effect on the server, unless it was explicitly enabled. A convenient way to enable a plugin XXX for specific tests is to create a have_XXX.opt file that contains necessary command-line options, and file that checks whether a plugin was loaded. Then any test that needs this plugin can source the file and have the plugin loaded automatically.


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