http://www.perlmonks.org?node_id=751639

andreas1234567 has asked for the wisdom of the Perl Monks concerning the following question:

Executive summary: Do not upgrade DBD::DB2 unless you have verified that your application works as expected with the new version. There is no test suite to help you detect errors or unexpected results.

DBD::DB2 is the database driver for IBM DB2 UDB. The database runs on a variety of platforms, including Unix (AIX), Windows, Linux and z/OS.

To my big surprise, DBD::DB2 has no real test suite, and recently there was discovered a bug where newer versions of the module return incorrect results for certain versions of the database for the clob data-type.

I claim that this bug could have easily been discovered during development if the module had even the simplest of tests (which in this case would be to insert a value, then retrieve the value, and test for equality), e.g. like this:

# -- Prepare test data: # create table dbddb2_clob ( # id integer not null, # data clob not null , # constraint pk_dbddb2_clob primary key (id) # ); # insert into dbddb2_clob values (1, 'fubar_clob'); my $sth = $dbh->prepare(q{select id,data from dbddb2_clob}); $sth->execute(); is_deeply($sth->fetchall_arrayref(), [[1,'fubar_clob']], q{Expect 1 row (1,'fubar_clob') returned});

Citing dhoss (here):

The benefit of test driven development is, you *know* your code will work before you ship it.
I will turn that around: The benefit of test driven development is, you detect when your code does not work as expected.

Let this serve as a reminder of how important it is to have a test suite, and a kind request to the module maintainers to start building one.

Update Fri Mar 20 12:21:46 CET 2009: The IBM OPENDEV team has responded to the bug and produced a patch that seems to fix the problem, and they deserve credit for doing so.