I can persist tabmanager state

tests/testclient/test_matches.py

@@ -3,7 +3,7 @@ from fastcore.basics import NotStr
 from fasthtml.components import *
 
 from myfasthtml.test.matcher import matches, StartsWith, Contains, DoesNotContain, Empty, DoNotCheck, ErrorOutput, \
-  ErrorComparisonOutput, AttributeForbidden, AnyValue
+  ErrorComparisonOutput, AttributeForbidden, AnyValue, NoChildren
 from myfasthtml.test.testclient import MyFT
 
 
@@ -24,6 +24,8 @@ from myfasthtml.test.testclient import MyFT
     ([Div(), Span()], DoNotCheck()),
     (NotStr("123456"), NotStr("123")),  # for NotStr, only the beginning is checked
     (Div(), Div(Empty())),
+    (Div(), Div(NoChildren())),
+    (Div(attr1="value"), Div(NoChildren())),
     (Div(attr1="value1"), Div(AttributeForbidden("attr2"))),
     (Div(123), Div(123)),
     (Div(Span(123)), Div(Span(123))),
@@ -54,6 +56,7 @@ def test_i_can_match(actual, expected):
     (Div(), Div(attr1=AnyValue()), "'attr1' is not found in Actual"),
     (NotStr("456"), NotStr("123"), "Notstr values are different"),
     (Div(attr="value"), Div(Empty()), "The condition 'Empty()' is not satisfied"),
+    (Div(Span()), Div(NoChildren()), "The condition 'NoChildren()' is not satisfied"),
     (Div(120), Div(Empty()), "The condition 'Empty()' is not satisfied"),
     (Div(Span()), Div(Empty()), "The condition 'Empty()' is not satisfied"),
     (Div(), Div(Span()), "Actual is lesser than expected"),
@@ -203,6 +206,7 @@ def test_i_can_output_error_child_element():
                                  ')',
                                  ]
 
+
 def test_i_can_output_error_child_element_text():
   """I can display error when the children is not a FT"""
   elt = Div("Hello world", Div(id="child_1"), Div(id="child_2"), attr1="value1")
@@ -217,6 +221,7 @@ def test_i_can_output_error_child_element_text():
                                  ')',
                                  ]
 
+
 def test_i_can_output_error_child_element_indicating_sub_children():
   elt = Div(P(id="p_id"), Div(Div(id="child_2"), id="child_1"), attr1="value1")
   expected = elt