如何构建一段时间内发生的进程的测试？

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>);