Added alert_dialog test

Author: FeodorFitsner

sdk/python/packages/flet/integration_tests/controls/golden/macos/alert_dialog/update_body_1.png

@@ -1,6 +1,9 @@
+import asyncio
+
+import pytest
+
 import flet as ft
 import flet.testing as ftt
-import pytest
 
 
 @pytest.mark.asyncio(loop_scope="module")
@@ -27,3 +30,54 @@ async def test_alert_dialog_basic(flet_app: ftt.FletTestApp, request):
             pixel_ratio=flet_app.screenshots_pixel_ratio
         ),
     )
+
+
+@pytest.mark.asyncio(loop_scope="module")
+async def test_update_body(flet_app: ftt.FletTestApp, request):
+    flet_app.page.theme_mode = ft.ThemeMode.LIGHT
+    ad = ft.AlertDialog(
+        key="ad",
+        title=ft.Text("Test"),
+        bgcolor=ft.Colors.YELLOW,
+        actions_alignment=ft.MainAxisAlignment.END,
+        actions=[
+            ok := ft.TextButton(
+                "OK",
+                visible=True,
+            ),
+            cancel := ft.TextButton(
+                "Cancel",
+                visible=True,
+            ),
+        ],
+    )
+    flet_app.page.enable_screenshots = True
+    flet_app.page.window.width = 400
+    flet_app.page.window.height = 600
+    flet_app.page.show_dialog(ad)
+    flet_app.page.update()
+    await flet_app.tester.pump_and_settle()
+    assert (await flet_app.tester.find_by_text("OK")).count == 1
+
+    flet_app.assert_screenshot(
+        "update_body_1",
+        await flet_app.page.take_screenshot(
+            pixel_ratio=flet_app.screenshots_pixel_ratio
+        ),
+    )
+
+    # change dialog color and hide "OK" button
+    await asyncio.sleep(1)
+    ad.bgcolor = ft.Colors.RED
+    ok.visible = not ok.visible  # hide button
+    cancel.disabled = not cancel.disabled  # disable button
+    flet_app.page.update()
+    await flet_app.tester.pump_and_settle()
+    assert (await flet_app.tester.find_by_text("OK")).count == 0
+
+    flet_app.assert_screenshot(
+        "update_body_2",
+        await flet_app.page.take_screenshot(
+            pixel_ratio=flet_app.screenshots_pixel_ratio
+        ),
+    )