Perl Hacks

Hack #68. Run Test Suites Persistently

Speed up your tests.

Large Perl applications with many interconnected modules can take a long time to start up. Perl needs to load, compile, and initialize all of the modules before it can start running your application.

Tests for a large system can be particularly slow. A test suite typically contains lots of small short-lived scripts, each of which pulls in lots of module code at start up. A few seconds of delay per script can add up to a lot of time spent waiting for your test suite to finish.

The cure for long startup times within web-based applications is to run under a persistent environment such as mod_perl or PersistentPerl. PersistentPerl works for command-line programs as well. It's usually as simple as changing the shebang line from #!/usr/bin/perl to #!/usr/bin/perperl.

Running your test suite persistently is slightly more complicated, and doesn't work for every test, but the benefit is a huge speed increase for most of your tests. Running your test suite persistently can speed up your tests by a factor of five on a slow machine.

The Hack

The first step of the hack is to make Test::Builder-based scripts compatible with PersistentPerl. There are several parts to this:

• The script has to reset the Test::Builder counter on startup.

• The script needs to prevent Test::Builder from duplicating STDOUT and STDERR, as this seems to be incompatible with PersistentPerl.

• Scripts with no_plan have to register a PersistentPerl cleanup handler to ...