test for center layout

tests/test_layouts_center.py

@@ -0,0 +1,33 @@
+from textual.geometry import Region, Size
+from textual.widget import Widget
+from textual.layouts.center import CenterLayout
+from textual._layout import WidgetPlacement
+
+
+def test_center_layout():
+
+    widget = Widget()
+    widget._size = Size(80, 24)
+    child = Widget()
+    child.styles.width = 10
+    child.styles.height = 5
+    layout = CenterLayout()
+
+    placements, widgets = layout.arrange(widget, [child], Size(60, 20))
+    assert widgets == {child}
+
+    expected = [
+        WidgetPlacement(
+            region=Region(x=25, y=7, width=10, height=5),
+            widget=child,
+            order=0,
+            fixed=False,
+        ),
+        WidgetPlacement(
+            region=Region(x=25, y=7, width=10, height=5),
+            widget=None,
+            order=0,
+            fixed=False,
+        ),
+    ]
+    assert placements == expected