test(v0): prove dynamic reusable row updates

Use one TodoRow projection for initial render and generated dynamic Vec<IntoEffect> row replacement batches, keeping the normal path on generated helpers instead of raw effects or registry plumbing.

req: canonical_authoring/003

examples/v0/src/main.rs

@@ -427,14 +427,28 @@ fn todos_view(todos: &[TodoRecord]) -> Todos {
     // req: html_safety/002 req: view/001 req: canonical_authoring/003
     Todos {
         summary: todo_summary(todos),
-        rows: todos
+        rows: todo_rows(todos),
+    }
+}
+
+#[cfg(test)]
+fn refresh_todo_rows_effect(todos: &[TodoRecord]) -> impl IntoEffect {
+    // req: canonical_authoring/003
+    let row_updates = todo_rows(todos)
+        .into_iter()
+        .map(|row| todos::todo_row.replace(row))
+        .collect::<Vec<_>>();
+    (row_updates, todos::summary.set(todo_summary(todos)))
+}
+
+fn todo_rows(todos: &[TodoRecord]) -> Vec<TodoRow> {
+    todos
         .iter()
         .map(|todo| TodoRow {
             id: TodoId(todo.id),
             title: todo.title.clone(),
         })
-            .collect(),
-    }
+        .collect()
 }
 
 fn todo_summary(todos: &[TodoRecord]) -> String {
@@ -587,6 +601,37 @@ mod tests {
             .is_none());
     }
 
+    // req: canonical_authoring/003 req: test/005
+    #[test]
+    fn reusable_todo_partial_supports_dynamic_replace_batches() {
+        let todos = vec![
+            TodoRecord {
+                id: 7,
+                title: "Ship v0".to_owned(),
+            },
+            TodoRecord {
+                id: 8,
+                title: "Write docs".to_owned(),
+            },
+        ];
+
+        let initial = ui::page(&todos_view(&todos));
+        let document = Html::parse_fragment(initial.as_str());
+        assert_eq!(
+            document
+                .select(&selector(&keyed_items_selector("li")))
+                .count(),
+            2
+        );
+
+        let refresh =
+            inspect_batch(refresh_todo_rows_effect(&todos).into_batch(ui::BUILD_FINGERPRINT));
+        assert_eq!(refresh.op_count(), 3);
+        assert!(refresh.replaces_keyed_html_containing(todos::todo_row, "7", "Ship v0"));
+        assert!(refresh.replaces_keyed_html_containing(todos::todo_row, "8", "Write docs"));
+        assert!(refresh.updates_text(todos::summary));
+    }
+
     // req: html_safety/002 req: view/001 req: test/005
     #[test]
     fn empty_todos_payload_is_rendered_by_a_hemplate_view() {