readonly(s) and some tests fixes

composer.json

@@ -66,7 +66,8 @@
         "allow-plugins": {
             "composer/package-versions-deprecated": true,
             "symfony/flex": true,
-            "symfony/runtime": true
+            "symfony/runtime": true,
+            "infection/extension-installer": true
         }
     },
     "autoload": {

src/Cheeper/Chapter7/Application/Author/Command/FollowCommandHandler.php

@@ -14,9 +14,9 @@ use Cheeper\Chapter7\DomainModel\Follow\FollowRepository;
 final class FollowCommandHandler
 {
     public function __construct(
-        private AuthorRepository $authors,
+        private readonly AuthorRepository $authors,
-        private FollowRepository $follows,
+        private readonly FollowRepository $follows,
-        private EventBus         $eventBus
+        private readonly EventBus         $eventBus
     ) {
     }
 
@@ -53,11 +53,11 @@ final class FollowCommandHandler
 
     private function notifyEvents(FollowCommand $command, array $domainEvents): void
     {
-        $stamppedEvents = array_map(
+        $stampedEvents = array_map(
             static fn ($event) => $event->stampAsResponseTo($command),
             $domainEvents
         );
 
-        $this->eventBus->notifyAll($stamppedEvents);
+        $this->eventBus->notifyAll($stampedEvents);
     }
 }

src/Cheeper/Chapter7/Application/Author/Command/SignUpCommandHandler.php

@@ -18,8 +18,8 @@ use Cheeper\Chapter7\DomainModel\Author\AuthorRepository;
 final class SignUpCommandHandler
 {
     public function __construct(
-        private AuthorRepository $authors,
+        private readonly AuthorRepository $authors,
-        private EventBus         $eventBus
+        private readonly EventBus         $eventBus
     ) {
     }
 
@@ -72,8 +72,14 @@ final class SignUpCommandHandler
         return null !== $inputWebsite ? Website::fromString($inputWebsite) : null;
     }
 
-    private function signUpAuthor(AuthorId $authorId, UserName $userName, EmailAddress $email, SignUpCommand $command, ?Website $website, ?BirthDate $birthDate): Author
+    private function signUpAuthor(
-    {
+        AuthorId $authorId,
+        UserName $userName,
+        EmailAddress $email,
+        SignUpCommand $command,
+        ?Website $website,
+        ?BirthDate $birthDate)
+    : Author {
         return Author::signUp(
             $authorId,
             $userName,

tests/Cheeper/Tests/Chapter7/Application/Author/Command/SignUpCommandHandlerTest.php

@@ -32,8 +32,6 @@ final class SignUpCommandHandlerTest extends TestCase
         $this->expectException(AuthorAlreadyExists::class);
         $this->expectExceptionMessage('Author with name "johndoe" already exists');
 
-        $eventBus = new InMemoryEventBus();
-
         $signUpHandler = new SignUpCommandHandler(
             $this->authorRepository,
             $this->eventBus
@@ -52,7 +50,7 @@ final class SignUpCommandHandlerTest extends TestCase
             )
         );
 
-        $eventBus->reset();
+        $this->eventBus->reset();
 
         $signUpHandler(
             new SignUpCommand(