How to structure tests for processes that occur over time? - php

Question

What is the approach for constructing tests of code that don't have an outcome in the immediate sense?
Let's say we have a very simple (yet quite rude) process:
User signs up to site
Two days pass
Send reminder email
Update some database fields
Ten days pass
Send "c'ya" email
Delete account
I can write tests for each set of sub tasks (email is sent, database is updated, etc). However how do I write well structured tests, that read something like:
"Two days after registration, reminder email should be sent"
"Ten days after registration, account is deleted"
Although I am using PHP and PHPUnit, I feel the question may/may not be language agnostic.

Answer 1

Based on implementation of your event mechanics. Like, when some event listener somewhere in your code receives event user:reminder with user id, then you need just:
1) Test reminder-send script by sending that event manually:
$eventBus->init();
$eventBus->attachListener($reminderListener);
$eventBus->fire(new ReminderEvent($user->id));
$this->expect(...); // reminder must be `sent`
2) Test generation of event when time had passed:
$time = now();
$delay = ...;
$emitter = new RemindEventEmitter($user->id, $time + $delay)
$eventBus->addEmitter($emitter);
$eventBus->setCurrentTime($time); // when we just registered emitter...
$eventBus->run();
$this->expectNot(...); // ... that event _must not_ be fired
$eventBus->setCurrentTime($time + $delay); // manually skip $delay time ...
$eventBus->run();
$this->expect(...); // test that event _must_ be fired
And that event-spawning/dispatching thing ($eventBus in my example) must relay on mockable/replacable time-getter:
// in production code
$eventBus->setCurrentTime(now());
// elsewhere in tests
$eventBus->setCurrentTime(<point in time you want to test against>);