[8.x] Add castAsJson method for database assertions (#34302)

* add `castAsJson` method for database assertions

database fields of type 'json' cannot be evaluted using strings, they must be cast to a database specific JSON type.

* Update InteractsWithDatabase.php

Co-authored-by: Taylor Otwell <taylor@laravel.com>

src/Illuminate/Foundation/Testing/Concerns/InteractsWithDatabase.php

@@ -5,6 +5,7 @@
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\SoftDeletes;
 use Illuminate\Support\Arr;
+use Illuminate\Support\Facades\DB;
 use Illuminate\Testing\Constraints\CountInDatabase;
 use Illuminate\Testing\Constraints\HasInDatabase;
 use Illuminate\Testing\Constraints\SoftDeletedInDatabase;
@@ -118,6 +119,19 @@ protected function isSoftDeletableModel($model)
             && in_array(SoftDeletes::class, class_uses_recursive($model));
     }
 
+    /**
+     * Cast a JSON string to a database compatible type.
+     *
+     * @param  array|string  $value
+     * @return \Illuminate\Database\Query\Expression
+     */
+    public function castAsJson($value)
+    {
+        $value = is_array($value) ? json_encode($value) : $value;
+
+        return DB::raw("CAST('$value' AS JSON)");
+    }
+
     /**
      * Get the database connection.
      *