Grouping tests with #[Group]

Last week I was building a new component for Cycle ORM — cycle/transaction. Naturally, I wrote its tests with Testo — and I immediately wanted to reproduce the approach I was used to in Cycle: run the same set of tests against every supported database. And that's when it turned out Testo was missing one thing I needed.

How tests are written in Cycle

Cycle's tests run on PHPUnit, and for the ones that hit real databases a handy convention has emerged:

• You write an abstract class with the tests;

• Then, for each driver, a final class extends it and wires up the concrete driver;

• The groups go on the final classes:

  /**
   * @group driver
   * @group driver-mysql
   */

  Here driver means the test talks to a database directly, while driver-mysql narrows it down to the concrete driver. The benefit is obvious: you can run tests on SQLite alone, or on any other driver of your choice. That's exactly how they're invoked in CI — a separate run for each database.

Groups in Testo

Testo didn't have test grouping yet — so it was time to add it. The whole thing took a few hours, including testing hypotheses and the final polish: the feature fit neatly into the Filter plugin.

Early on I noticed one detail: the driver group in my tests could be moved up to the parent class instead of being duplicated in every child. So I added group inheritance right away.

Groups here are plain string labels you attach with the #[Group]#[Group(string ...$names)]Labels a class, method, or function with one or more group names for selective filtering. attribute. The same scenario with an abstract class and drivers now looks like this:

#[Group('driver')]
abstract class TransactionTestCase
{
    public function commitsTransaction(): void { /* ... */ }
}

#[Test]
#[Group('driver-mysql')]
final class MySqlTransactionTest extends TransactionTestCase {}

#[Test]
#[Group('driver-sqlite')]
final class SqliteTransactionTest extends TransactionTestCase {}

You pick groups at launch with the --group flag:

# SQLite tests only
testo run --group=driver-sqlite

# All tests that hit a database directly
testo run --group=driver

# Everything except the slow ones
testo run --group=!slow

An unexpected twist

Honestly, I considered test grouping a routine feature and didn't make much of it — I wasn't even going to write a separate post. But today I sat down to read the feedback from the beta launch and stumbled on the fact that group inheritance had been requested in PHPUnit as far back as 2019 — only to be turned down:

I am sorry to say this, but me this does not sound useful. Inherit groups from parent classes #3935

Funnily enough, this exact feature came in handy the very first time I used the #[Group]#[Group(string ...$names)]Labels a class, method, or function with one or more group names for selective filtering. attribute.

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So here I am, reminding you of one simple thing: Testo is built around what developers actually need.

If an existing tool doesn't solve the community's problems, a new one is only a matter of time. That's how Testo came to be.

Bring your ideas and needs to Testo — they stand every chance of getting built. And even if you don't use it, keep this in mind: features from Testo trickle into PHPUnit too, just with a delay.