add Slider tests

Author: OwenMcDonnell

sdk/python/packages/flet/integration_tests/controls/golden/macos/slider/basic.png

@@ -0,0 +1,20 @@
+import pytest
+
+import flet as ft
+import flet.testing as ftt
+
+
+@pytest.mark.asyncio(loop_scope="module")
+async def test_basic(flet_app: ftt.FletTestApp, request):
+    await flet_app.assert_control_screenshot(
+        request.node.name,
+        ft.Slider(value=0.3),
+    )
+
+
+@pytest.mark.asyncio(loop_scope="module")
+async def test_range_and_label(flet_app: ftt.FletTestApp, request):
+    await flet_app.assert_control_screenshot(
+        request.node.name,
+        ft.Slider(min=0, max=100, divisions=10, label="{value}%"),
+    )