add test

app/Http/Controllers/TimeTrackerController.php

@@ -53,7 +53,7 @@ class TimeTrackerController extends Controller
      */
     public function show(TimeTracker $timeTracker)
     {
-        //
+        return response()->json(new TimeTrackerResource($timeTracker->load('toDo')));
     }
 
     /**

app/Http/Resources/ToDoResource.php

@@ -19,7 +19,7 @@ class ToDoResource extends JsonResource
             'user_id' => $this->user_id,
             'name' => $this->name,
             'description' => $this->description,
-            'checked' => $this->checked,
+            'checked' => $this->checked?->format('Y-m-d H:i:s'),
             'duration' => $this->duration,
         ];
     }

app/Models/ToDo.php

@@ -17,6 +17,10 @@ class ToDo extends Model
         'description',
     ];
 
+    protected $casts = [
+        'checked' => 'datetime',
+    ];
+
     public function user(): BelongsTo
     {
         return $this->belongsTo(User::class);