What causes "Event class "%s" does not exist" in sebastianbergmann/phpunit?

Create the event class or fix the FQCN; prefer MyEvent::class over string literals so the IDE and PHP verify it.

sebastianbergmann/phpunit · error · UnknownEventException

Event class "%s" does not exist

Error message

Event class "%s" does not exist

What it means

The second argument of TypeMap::addMapping() must be an existing class name; ensureEventClassExists() throws UnknownEventException when class_exists() fails (including its autoload attempt). It runs before the Event-interface check, so a missing class is reported distinctly from a class that exists but does not implement Event.

Source

Thrown at src/Event/TypeMap.php:114

        if (!interface_exists($subscriberInterface)) {
            throw new UnknownSubscriberException(
                sprintf(
                    'Subscriber "%s" does not exist or is not an interface',
                    $subscriberInterface,
                ),
            );
        }
    }

    /**
     * @param class-string $eventClass
     *
     * @throws UnknownEventException
     */
    private function ensureEventClassExists(string $eventClass): void
    {
        if (!class_exists($eventClass)) {
            throw new UnknownEventException(
                sprintf(
                    'Event class "%s" does not exist',
                    $eventClass,
                ),
            );
        }
    }

    /**
     * @param class-string $subscriberInterface
     *
     * @throws InvalidSubscriberException
     */
    private function ensureSubscriberInterfaceExtendsInterface(string $subscriberInterface): void
    {
        if (!in_array(Subscriber::class, class_implements($subscriberInterface), true)) {
            throw new InvalidSubscriberException(
                sprintf(

View on GitHub (pinned to f123cdb2a2)

Solutions

Create the event class or fix the FQCN; prefer MyEvent::class over string literals so the IDE and PHP verify it.
Verify with class_exists(MyEvent::class) in the same process/autoloader context if unsure.
Run 'composer dump-autoload' (or install the missing package) and retry.

Example fix

// before
$typeMap->addMapping(MySubscriberInterface::class, 'App\Event\OrderPlaced'); // literal, class in App\Events\

// after
use App\Events\OrderPlaced;

$typeMap->addMapping(MySubscriberInterface::class, OrderPlaced::class);

Defensive patterns

Strategy: validation

Validate before calling

if (!class_exists($eventClass)) {
    throw new InvalidArgumentException($eventClass . ' does not exist; create the class or fix the FQCN');
}

$typeMap->addMapping($subscriberInterface, $eventClass);

Type guard

/** @phpstan-assert class-string $name */
function assertClassExists(string $name): void
{
    if (!class_exists($name)) {
        throw new InvalidArgumentException("Class '{$name}' does not exist");
    }
}

Prevention

Use MyEvent::class instead of string literals for event class arguments.
Create the event class before wiring its mapping.
Verify autoloading in the same process context when registration is dynamic.

When it happens

Trigger: addMapping(MySubscriberInterface::class, 'App\Event\ThingHappened') where ThingHappened is misspelled, not yet created, or defined in a package that is not installed; case mismatches in namespace segments on case-sensitive filesystems.

Common situations: Custom event development where the mapping is wired before the event class is written; refactors that rename event classes without updating registration code; partial vendor trees after a failed 'composer install'; stale opcache after moving files.

Related errors

AI-assisted analysis of sebastianbergmann/phpunit@f123cdb2a2 (2026-08-23). Data as JSON: /api/errors/604f1683e013cb79. Report an issue: GitHub.