ref(container): split size and position calculations

src/testing.zig

@@ -34,7 +34,7 @@ pub const Renderer = struct {
 
     pub fn resize(this: *@This(), size: Point) !void {
         this.size = size;
-        const n = @as(usize, size.cols) * @as(usize, size.y);
+        const n = @as(usize, size.x) * @as(usize, size.y);
 
         this.allocator.free(this.screen);
         this.screen = this.allocator.alloc(Cell, n) catch @panic("testing.zig: Out of memory.");
@@ -120,8 +120,8 @@ pub fn expectContainerScreen(size: Point, container: *Container(event.SystemEven
     var renderer: Renderer = .init(allocator, size);
     defer renderer.deinit();
 
-    container.reposition(.{});
-    container.resize(size);
+    try renderer.resize(size);
+    container.resize(.{}, size);
     try renderer.render(Container(event.SystemEvent), container);
 
     try expectEqualCells(.{}, renderer.size, expected, renderer.screen);