Just a Theory

By David E. Wheeler

Posts about Test-Driven Database Design

Introducing MyTAP

I gave my OSCON tutorial (slides) last week. It went okay. I spent way too much time helping to get everyone set up with pgTAP, and then didn’t have time to have the attendees do the exercises, and I had to rush through 2.5 hours of material in 1.5 hours. Yikes! At least the video will be better when it’s released (more when that happens).

But as often happens, I was asked whether something like pgTAP exists for MySQL. But this time I was asked by MySQL Community Manager Giuseppe Maxia, who also said that he’d tried to create a test framework himself (a fellow Perl hacker!), but that it wasn’t as nice as pgTAP. Well, since I was at OSCON and tend to like to hack on side projects while at conferences, and since I hoped that Giuseppe will happily take it over once I’ve implemented the core, I started hacking on it myself. And today, I’m pleased to announce the release of MyTAP 0.01 (downloads).

Once you’ve downloaded it, install it against your MySQL server like so:

mysql -u root < mytap.sql

Here’s a very simple example script:

-- Start a transaction.

-- Plan the tests.
SELECT tap.plan(1);

-- Run the tests.
SELECT tap.pass( 'My test passed, w00t!' );

-- Finish the tests and clean up.
CALL tap.finish();

You can run this test from a .sql file using the mysql client like so:

mysql -u root --disable-pager --batch --raw --skip-column-names --unbuffered --database try --execute 'source test.sql'

But that’s a PITA and can only run one test at a time. Instead, put all of your tests into a directory, perhaps named tests, each with the suffix “.my”, and use my_prove (install TAP::Parser::SourceHandler::MyTAP from CPAN to get it) instead:

my_prove -u root --database try tests/

For MyTAP’s own tests, the output looks like this:

tests/eq.my ........ ok
tests/hastap.my .... ok
tests/matching.my .. ok
tests/moretap.my ... ok
tests/todotap.my ... ok
tests/utils.my ..... ok
All tests successful.
Files=6, Tests=137,  1 wallclock secs
(0.06 usr  0.03 sys +  0.01 cusr  0.02 csys =  0.12 CPU)
Result: PASS

Nice, eh? Of course there are quite a few more assertion functions. See the complete documentation for details.

Now, I did my best to keep the interface the same as pgTAP, but there are a few differences:

  • MySQL temporary tables are teh suck, so I had to use permanent tables to track test state. To make this more feasible, MyTAP is always installed in its own database, (named “tap” by default), and you must always schema-qualify your use of the MyTAP functions.
  • Another side-effect of permanent tables is that MyTAP must keep track of test outcomes without colliding with the state from tests running in multiple concurrent connections. So MyTAP uses connection_id() to keep track of state for a single test run. It also deletes the state when tests finish(), but if there’s a crash before then, data can be left in those tables. If the connection ID is ever re-used, this can lead to conflicts. This seems mostly avoidable by using InnoDB tables and transactions in the tests.
  • The word “is” is strictly reserved by MySQL, so the function that corresponds to pgTAP’s is() is eq() in MyTAP. Similarly, isnt() is called not_eq() in MyTAP.
  • There is no way to throw an exception in MySQL functions an procedures, so the code cheats by instead performing an illegal operation: selecting from a non-existent column, where the name of that column is the error message. Hinky, but should get the point across.

Other than these issues, things went fairly smoothly. I finished up the 0.01 version last night and released it today with most of the core functionality in place. And now I want to find others to take over, as I am not a MySQL hacker myself and thus unlikely ever to use it. If you’re interested, my recommendations for things to do next are:

So fork on GitHub or contact me if you’d like to be added as a collaborator (I’m looking at you, Giuseppe!).

Hope you find it useful.

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Important Announcement at OSCON Next Week

Flipr Antisocial Networking

Logo design by Strongrrl.

A sneak peak at what I’m working on for my tutorial session at OSCON. Be there at 8:30 Monday morning for the important details. You’re sure to find my new venture exciting—perhaps the most important social media announcement of 2010. You can’t afford to miss that, can you?

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