Implemented testing functions

src/myfasthtml/core/testclient.py

@@ -1,3 +1,4 @@
+import dataclasses
 import json
 import uuid
 from dataclasses import dataclass
@@ -15,6 +16,8 @@ from myfasthtml.core.commands import mount_commands
 class MyFT:
   tag: str
   attrs: dict
+  children: list['MyFT'] = dataclasses.field(default_factory=list)
+  text: str | None = None
 
 
 class TestableElement: