Code size of an engine versus test suite

If you count the lines of code in the MySQL Cluster (NDB) test suite (mysql-5.1/storage/ndb/test – and exclude the old ODBC stuff) you come up with about 104000 lines of code. This is in contrast to the approximate other 350,000 lines of code for the NDB engine (excluding the handler, which is an additional 12,000 lines – this isn’t tested much by the NDB test suite… is meant to take care of a lot of that).

If you go and check the MyISAM tree, it’s only 40545 lines of code – for the entire engine. That’s right, the MySQL Cluster test suite is about 2.5 times the size of MyISAM.

If you look at tests, which are just lists of SQL commands with static data, it comes up at 250,000 lines (that excludes result files). The NDB tests do things programmatically – so can generate large amounts of data and different loads quite easily.

The architecture of the NDB tests (commonly referred to as autotest, ATRT or HUGO framework) is very different from – it easily allows you to write a test that is high on concurrency, high on load and high on amount of data. It also is modular, so that when you get an issue from a customer (or need to do some benchmarking on a speficic type of schema) you can use the utility programs to help you (e.g. there’s one that does random PK updates to tables, one that does scans, one that does index operations etc).

There’s this whole bunch of things you just cannot do with

Then we get to fault injection… MySQL Cluster is a distributed system that is designed to withstand failure. Without testing this, we can never say it’s remotely HA. So we test it. A lot. We inject failures into nodes to check our node failure handling, using the utility programs and some basic shell it’s possible to do custom tests (such as multi-node failure)  where our test suite doesn’t have the best coverage yet.

Again, either not possible or extremely hard with

mysql_slap is the hint of a nice utility to help in testing… but using it in scripts in a verifyable way (i.e. check what came out is what went in, using a variety of access methods – full table scans, pk scans, index scans, stored procs, cursors, views, joins etc) is tricky at best (but really impossible).

Yes, I’m really pining for a better test suite infrastructure for the MySQL Server – it can only lead to better quality software…. almost somebody just rewriting a bunch of the hugo classes to use the MySQL C API would be useful.

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