Testing Events

Most modules/plugins support events that are triggered that enable modules/plugins to place event listeners which modify actions and behaviours. This increases the flexibility and usability of modules/plugins.

Seeing as events and the triggering thereof are routed through some complex Yii2 (opens new window) based functionality some specific steps must be taken to test code that triggers events.

# Testing Event Code

Craft provides a simple helper method that allows you to test event codes. Firstly you need to ensure that your test class has a $tester property. Once this class property is declared you can call the following method:

$this->tester->expectEvent(MyComponent::class, MyComponent::AN_EVENT, function() {
  • The first argument is the class from which your event gets triggered. Similarly to the first argument you pass when calling $this->trigger() from a class that extends craft\base\Component.

  • The second argument is the name of your event. Similarly to the second argument you pass when calling $this->trigger() from a class that extends craft\base\Component.

  • The third argument is is a closure that must contain the code to trigger an event. If the callback does not trigger the event the test will fail.

This is a watered down example of the expectEvent method. There are two optional parameters that give you a whole lot of extra power - see below.

# Additional Properties

If you want more fine-grained control over your event testing code the expectEvent method has two optional parameters.

# string $eventInstance = ''

The this is the fourth property of expectEvent. If you want to check the class of the event that was passed you can set this property. The property will be compared using instanceof (opens new window).

# array $eventValues = []

The eventValues property accepts an array that can be specially setup to validate the properties of the event that was passed.

# Setting up $eventValues

Craft provides a special helper method that is recommended to configure $eventValues. You can call $this->tester->createEventItems() and pass in an array with the following keys:

# eventPropName

The name of the event property you want to test. I.E. if you want to check the name of yii\base\Event you would set this to 'name'.

# type

You can choose from the following:

use craft\test\EventItem;


use craft\test\EventItem;


  • TYPE_CLASS instructs Craft that when we access the $eventPropName on the passed event an object will be returned.
  • TYPE_OTHERVALUE instructs Craft to accept any non-object value.

# desiredClass

If you have set TYPE_CLASS you can pass in an additional desiredClass property. Craft will then compare the returned object to the desiredClass property using instanceof.

# desiredValue

desiredValue is designed to check the property values of the event that is passed. This can depend based on the type argument:

# When Type is EventItem::TYPE_OTHERVALUE

Here you can set the desiredValue to anything you want. The result of accessing the event using the eventPropName property will be directly compared using assertSame().

# When Type is EventItem::TYPE_CLASS

Craft allows you to check the individual properties of the returned object. In order to do this you must enter a key-value array where:

  • key Is the name of a property belonging to the object that was returned when accessing the event using eventPropName.

  • value The value that the above property above should be set to.

See a complete example below:

use yii\base\Event;
use craft\test\EventItem;

$this->tester->expectEvent(SomeComponent::class, SomeComponent::SOME_EVENT, function() {

        // Code that should trigger an event goes here.

    }, Event::class,
            // The $event->sender prop is a \stdClass where the $key property is set to 'value'
            'eventPropName' => 'sender',
            'type' => EventItem::TYPE_CLASS,
            'desiredClass' => \stdClass::class,
            'desiredValue' => [
                'key' => 'value'
            // The $event->name prop string set to 'someEvent'.
            'eventPropName' => 'name',
            'type' => EventItem::TYPE_OTHERVALUE,
            'desiredValue' => 'someEvent'