Clock

We have a Clock interface which enables you to replace the actual clock implementation in your services for testing purposes. We are using this clock to create the recorded_on datetime for the events.

Note

The Clock interface is PSR-20 compatible. For more information see here.

SystemClock

This uses the native system clock to return the DateTimeImmutable instance - in this case new DateTimeImmutable().

use Patchlevel\EventSourcing\Clock\SystemClock;

$clock = new SystemClock();
$date = $clock->now(); // get the actual datetime 
$date2 = $clock->now();

$date == $date2 // false
$date === $date2 // false

FrozenClock

This implementation should only be used for the tests. This enables you to freeze the time and with that to have deterministic tests.

use Patchlevel\EventSourcing\Clock\FrozenClock;

$date = new DateTimeImmutable();

$clock = new FrozenClock($date);
$frozenDate = $clock->now(); // gets the date provided before 

$date == $frozenDate // true
$date === $frozenDate // false

The FrozenClock can also be updated with a new date, so you can test a jump in time.

use Patchlevel\EventSourcing\Clock\FrozenClock;

$firstDate = new DateTimeImmutable();
$clock = new FrozenClock($firstDate);

$secondDate = new DateTimeImmutable();
$clock->update($secondDate);

$frozenDate = $clock->now();

$firstDate == $frozenDate // false
$secondDate == $frozenDate // true

Note

The instance of the frozen datetime will be cloned internally, so the it's not the same instance but equals.