Musings on Koha’s database-dependent tests

One number I quite like today is 99. That’s the difference between the count of explicitly enumerated tests in Koha’s master branch as of 19 May (1,837) and the count today (1,936)¹. So far in the 3.14 cycle, eleven people have contributed patches that touch t/.

In particular, there’s been quite a bit of work on the database-dependent test suite that has increased both its coverage and its usability. Database-dependent test cases are useful for several reasons. First, a good bit of Koha’s code simply cannot be tested under realistic conditions if a Koha database isn’t available to talk to; while DBD::Mock can be use to mock query responses, it can be tedious to write the mocks. Second, test scripts that can use a database can readily exercise not just individual routines, but higher-level workflows. For example, it would be feasible to write a set of tests that creates a loan, renews it, simulates it becoming overdue, charges overdue fines, then returns the loan. In turn, being able to test larger sequences of actions can make it easier to avoid cases where a seemingly innocuous change to one core routine has an unanticipated effect elsewhere. This consideration particularly matters for Koha’s circulation code.

The automated buildbot has been running the DB-dependent tests for some time, but it’s historically been a dicier proposition for the average Koha hacker to run them on their own development databases. On the one hand, you probably don’t want to risk letting a test case mess up your database. On the other hand, some of the test cases make assumptions about the initial state of the database that may be unwarranted.

Although letting the buildbot do its thing is good, test cases are most useful if developers are able and willing to run them at any time. Worrying about damage to your development DB or having to figure out fiddly preconditions both decrease the probability that the tests will be run.

Recently, a simple “trick” has been adopted to deal with the first concern: make each DB-dependent test script operate in a transaction that gets rolled back. This is simple to set up:

use Modern::Perl;
use C4::Context;
use Test::More tests => 5;

my $dbh = C4::Context->dbh;
# Start transaction
$dbh->{AutoCommit} = 0;
$dbh->{RaiseError} = 1;

# Testy-testy test test test

$dbh->rollback();

The trick lies in setting AutoCommit on the database handle to 0. Setting RaiseError will cause the test script to abort if a fatal SQL error is raised. The $dbh->rollback() at the end is optional; if you let the script fall through to the end, or if the script terminates unexpectedly, the transaction will get rolled back regardless.

Doing all of the tests inside of a transaction grants you … freedom. Testing circulation policies? You can empty out issuingrules, set up a set of test policies, run through the variations, then end the test script confident that your original loan rules will be back in place.

It also grants you ease. Although it’s a good idea for Koha to let you easily run the tests in a completely fresh database, test cases that can run in your main development database are even better.

This ties into the second concern, which is being addressed by an ongoing project which Jonathan Druart and others have been working on to make each test script create the test data it needs. For example, if a test script needs a patron record, it will add it rather than assume that the database contains one. The DB-dependent tests currently do make a broader assumption that some of the English-language sample data has been loaded (most notably the sample libraries), but I’m confident that that will be resolved by the time 3.14 is released.

I’m seeing a virtuous cycle starting to develop: the safer it gets for Koha devs to run the tests, the more that they will be run — and the more that will get written. In turn, the more test coverage we achieve, the more confidently we can do necessary refactoring. In addition, the more tests we have, the more documentation — executable documentation! — we’ll have of Koha’s internals.

---

Musings on Koha’s database-dependent tests by Galen Charlton is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.