add find method to node repo and impl to fake repo

app/Node/NodeRepository.php

@@ -7,4 +7,6 @@ use App\Node\Node;
 interface NodeRepository
 {
     public function create(CreateNodeDto $dto): Node;
+
+    public function find(int $id): ?Node;
 }

tests/Fakes/FakeNodeRepository.php

@@ -8,11 +8,44 @@ use App\Node\NodeRepository;
 
 class FakeNodeRepository implements NodeRepository
 {
+    private array $existingNodes = [];
+
     public function create(CreateNodeDto $dto): Node
     {
-        return new Node(
+        $id = $this->nextId();
+        $node = new Node(
+            id: $id,
             text: $dto->text,
             title: $dto->title,
+            parentNode: $dto->parentNode,
+        );
+        $this->existingNodes[$id] = $node;
+
+        return $node;
+    }
+
+    private function nextId(): int
+    {
+        return count($this->existingNodes);
+    }
+
+    public function find(int $id): ?Node
+    {
+        $node = array_find(
+            $this->existingNodes,
+            function (Node $node) use ($id) {
+                return $node->getId() === $id;
+            }
+        );
+        if ($node === null) {
+            return nullj;
+        }
+
+        return new Node(
+            id: $id,
+            title: $node->getTitle(),
+            text: $node->getText(),
+            parentNode: $node->getParentNode(),
         );
     }
 }