fix test warning for undefined array key by using array_find

app/Text/Text.php

@@ -9,6 +9,11 @@ class Text
         private string $name,
     ) {}
 
+    public function getId(): int
+    {
+        return $this->id;
+    }
+
     public function getName(): string
     {
         return $this->name;

tests/Fakes/FakeTextRepository.php

@@ -27,7 +27,12 @@ class FakeTextRepository implements TextRepository
 
     public function find(int $id): ?Text
     {
-        $text = $this->existingTexts[$id];
+        $text = array_find(
+            $this->existingTexts,
+            function (Text $text) use ($id){
+                return $text->getId() === $id;
+            }
+        );
         if ($text === null) {
             return null;
         }