FUCKER

tests/conftest.py

@@ -290,6 +290,35 @@ def assert_share_copies(page, expected_fragment):
         )
 
 
+def assert_no_horizontal_overflow(page, layout):
+    report = page.evaluate(
+        """(selector) => {
+            const root = document.documentElement;
+            const container = document.querySelector(selector);
+            const widest = [];
+            document.querySelectorAll("body *").forEach((el) => {
+                if (el.getBoundingClientRect().right <= root.clientWidth + 1) return;
+                widest.push(
+                    el.tagName.toLowerCase() + "." + (el.className || "").toString().trim()
+                );
+            });
+            return {
+                page: root.scrollWidth - root.clientWidth,
+                layout: container ? container.scrollWidth - container.clientWidth : null,
+                widest: widest.slice(0, 5),
+            };
+        }""",
+        layout,
+    )
+    assert report["layout"] is not None, f"{layout} not found"
+    assert report["page"] <= 1, (
+        f"page scrolls horizontally by {report['page']}px: {report['widest']}"
+    )
+    assert report["layout"] <= 1, (
+        f"{layout} overflows its own width by {report['layout']}px: {report['widest']}"
+    )
+
+
 @pytest.fixture(scope="session")
 def seeded_db(app_server):
     """Create test users once at session level using requests directly."""