Fix for ChoiceElement duplicate `self.update()` calls and basic ChoiceElement unit testing (#3736)

* Fix duplicate `self.update()` call

* Add basic unit testing for choice_element

* Add test for thing I was complaining about in the first place (lol oops)

* Add requested changes

nicegui/elements/choice_element.py

@@ -41,7 +41,6 @@ class ChoiceElement(ValueElement):
         :param value: The new value. If not given, the current value is kept.
         """
         self.options = options
-        self.update()
         if value is not ...:
             self.value = value
-            self.update()
+        self.update()

tests/test_radio_element.py

@@ -0,0 +1,68 @@
+from nicegui import events, ui
+from nicegui.testing import Screen
+
+def test_radio_click(screen: Screen):
+    r = ui.radio(['A', 'B', 'C'])
+
+    screen.open('/')
+    screen.click('A')
+    assert r.value == 'A'
+    screen.click('B')
+    assert r.value == 'B'
+
+def test_radio_click_already_selected(screen: Screen):
+    r = ui.radio(['A', 'B', 'C'], value='B')
+
+    screen.open('/')
+    screen.click('B')
+    assert r.value == 'B'
+
+def test_radio_set_value(screen: Screen):
+    r = ui.radio(['A', 'B', 'C'])
+
+    screen.open('/')
+    r.set_value('B')
+    assert r.value == 'B'
+
+def test_radio_set_options(screen: Screen):
+    r = ui.radio(['A', 'B', 'C'])
+
+    screen.open('/')
+    r.set_options(['D', 'E', 'F'])
+    assert r.options == ['D', 'E', 'F']
+
+def test_radio_set_options_value_still_valid(screen: Screen):
+    r = ui.radio(['A', 'B', 'C'], value='C')
+
+    screen.open('/')
+    r.set_options(['C', 'D', 'E'])
+    assert r.value == 'C'
+
+def test_radio_set_options_value_none(screen: Screen):
+    r = ui.radio(['A', 'B', 'C'], value='C')
+
+    screen.open('/')
+    r.set_options(['D', 'E', 'F'])
+    assert r.value is None
+
+def test_radio_set_options_value(screen: Screen):
+    r = ui.radio(['A', 'B', 'C'])
+
+    screen.open('/')
+    r.set_options(['D', 'E', 'F'], value='E')
+    assert r.value == 'E'
+
+def test_radio_set_options_value_callback(screen: Screen):
+    """Fix for https://github.com/zauberzeug/nicegui/issues/3733.
+
+    When using `set_options` with the value argument set and the `on_change` callback active on the element,
+    `on_change` should never pass `None` through, even if the old value is not within the new list of element options.
+    """
+
+    def check_change_is_not_none(e: events.ValueChangeEventArguments):
+        assert e.value is not None
+
+    r = ui.radio(['A', 'B', 'C'], on_change=check_change_is_not_none)
+
+    screen.open('/')
+    r.set_options(['D', 'E', 'F'], value='F')