Make the widget moving tests more granular and add more tests

Adds two (currently xfail) tests to illustrate #1743

tests/test_widget_child_moving.py

@@ -1,58 +1,92 @@
+from __future__ import annotations
+
 import pytest
 
 from textual.app import App
 from textual.widget import Widget, WidgetError
 
 
-async def test_widget_move_child() -> None:
+async def test_move_child_no_direction() -> None:
     """Test moving a widget in a child list."""
-
-    # Test calling move_child with no direction.
     async with App().run_test() as pilot:
         child = Widget(Widget())
         await pilot.app.mount(child)
         with pytest.raises(WidgetError):
             pilot.app.screen.move_child(child)
 
-    # Test calling move_child with more than one direction.
+
+async def test_move_child_both_directions() -> None:
+    """Test calling move_child with more than one direction."""
     async with App().run_test() as pilot:
         child = Widget(Widget())
         await pilot.app.mount(child)
         with pytest.raises(WidgetError):
             pilot.app.screen.move_child(child, before=1, after=2)
 
-    # Test attempting to move a child that isn't ours.
+
+async def test_move_child_not_our_child() -> None:
+    """Test attempting to move a child that isn't ours."""
     async with App().run_test() as pilot:
         child = Widget(Widget())
         await pilot.app.mount(child)
         with pytest.raises(WidgetError):
             pilot.app.screen.move_child(Widget(), before=child)
 
-    # Test attempting to move relative to a widget that isn't a child.
+
+async def test_move_child_to_outside() -> None:
+    """Test attempting to move relative to a widget that isn't a child."""
     async with App().run_test() as pilot:
         child = Widget(Widget())
         await pilot.app.mount(child)
         with pytest.raises(WidgetError):
             pilot.app.screen.move_child(child, before=Widget())
 
-    # Make a background set of widgets.
-    widgets = [Widget(id=f"widget-{n}") for n in range(10)]
 
-    # Test attempting to move past the end of the child list.
+@pytest.mark.xfail(
+    strict=True, reason="https://github.com/Textualize/textual/issues/1743"
+)
+async def test_move_child_before_itself() -> None:
+    """Test moving a widget before itself."""
     async with App().run_test() as pilot:
+        child = Widget(Widget())
+        await pilot.app.mount(child)
+        pilot.app.screen.move_child(child, before=child)
+
+
+@pytest.mark.xfail(
+    strict=True, reason="https://github.com/Textualize/textual/issues/1743"
+)
+async def test_move_child_after_itself() -> None:
+    """Test moving a widget after itself."""
+    async with App().run_test() as pilot:
+        child = Widget(Widget())
+        await pilot.app.mount(child)
+        pilot.app.screen.move_child(child, after=child)
+
+
+async def test_move_past_end_of_child_list() -> None:
+    """Test attempting to move past the end of the child list."""
+    async with App().run_test() as pilot:
+        widgets = [Widget(id=f"widget-{n}") for n in range(10)]
         container = Widget(*widgets)
         await pilot.app.mount(container)
         with pytest.raises(WidgetError):
             container.move_child(widgets[0], before=len(widgets) + 10)
 
-    # Test attempting to move before the end of the child list.
+
+async def test_move_before_end_of_child_list() -> None:
+    """Test attempting to move before the end of the child list."""
     async with App().run_test() as pilot:
+        widgets = [Widget(id=f"widget-{n}") for n in range(10)]
         container = Widget(*widgets)
         await pilot.app.mount(container)
         with pytest.raises(WidgetError):
             container.move_child(widgets[0], before=-(len(widgets) + 10))
 
-    # Test the different permutations of moving one widget before another.
+
+async def test_move_before_permutations() -> None:
+    """Test the different permutations of moving one widget before another."""
+    widgets = [Widget(id=f"widget-{n}") for n in range(10)]
     perms = ((1, 0), (widgets[1], 0), (1, widgets[0]), (widgets[1], widgets[0]))
     for child, target in perms:
         async with App().run_test() as pilot:
@@ -63,7 +97,10 @@ async def test_widget_move_child() -> None:
             assert container._nodes[1].id == "widget-0"
             assert container._nodes[2].id == "widget-2"
 
-    # Test the different permutations of moving one widget after another.
+
+async def test_move_after_permutations() -> None:
+    """Test the different permutations of moving one widget after another."""
+    widgets = [Widget(id=f"widget-{n}") for n in range(10)]
     perms = ((0, 1), (widgets[0], 1), (0, widgets[1]), (widgets[0], widgets[1]))
     for child, target in perms:
         async with App().run_test() as pilot:
@@ -74,16 +111,22 @@ async def test_widget_move_child() -> None:
             assert container._nodes[1].id == "widget-0"
             assert container._nodes[2].id == "widget-2"
 
-    # Test moving after a child after the last child.
+
+async def test_move_child_after_last_child() -> None:
+    """Test moving after a child after the last child."""
     async with App().run_test() as pilot:
+        widgets = [Widget(id=f"widget-{n}") for n in range(10)]
         container = Widget(*widgets)
         await pilot.app.mount(container)
         container.move_child(widgets[0], after=widgets[-1])
         assert container._nodes[0].id == "widget-1"
         assert container._nodes[-1].id == "widget-0"
 
-    # Test moving after a child after the last child's numeric position.
+
+async def test_move_child_after_last_numeric_location() -> None:
+    """Test moving after a child after the last child's numeric position."""
     async with App().run_test() as pilot:
+        widgets = [Widget(id=f"widget-{n}") for n in range(10)]
         container = Widget(*widgets)
         await pilot.app.mount(container)
         container.move_child(widgets[0], after=widgets[9])