Improve some coverage in integration form

frontend/src/utils/contactMerge.ts

@@ -0,0 +1,25 @@
+import type { Contact } from '../types';
+
+/**
+ * Merge an incoming contact into an existing list.
+ *
+ * - If the contact exists (matched by public_key), merge fields and return
+ *   a new array only if something changed (preserves referential equality
+ *   for React when nothing changed).
+ * - If the contact is new, append it.
+ */
+export function mergeContactIntoList(contacts: Contact[], incoming: Contact): Contact[] {
+  const idx = contacts.findIndex((c) => c.public_key === incoming.public_key);
+  if (idx >= 0) {
+    const existing = contacts[idx];
+    const merged = { ...existing, ...incoming };
+    const unchanged = (Object.keys(merged) as (keyof Contact)[]).every(
+      (k) => existing[k] === merged[k]
+    );
+    if (unchanged) return contacts;
+    const updated = [...contacts];
+    updated[idx] = merged;
+    return updated;
+  }
+  return [...contacts, incoming];
+}