Verify Accept delivery in relay approval tests

Record deliveries to Alice's inbox and assert that approved follows
produce exactly one Accept POST from the relay for the expected Follow.
Cover subscription approval, public follows, and malformed follower rows.
Use unique Follow IDs to isolate concurrent tests and loop iterations.

#1046

Validated with mise run test-each relay, including code checks and
Deno, Node.js, and Bun tests.

Changelog: none
Assisted-by: Codex:gpt-6-astra

Author: sij411

packages/relay/src/litepub.test.ts

@@ -142,6 +142,25 @@ function recordInbox(inbox: string): DeliveredRequest[] {
   return recorded;
 }
 
+const aliceDeliveries = recordInbox(aliceInbox);
+
+function assertAcceptDelivered(
+  follow: Follow,
+  deliveries: readonly DeliveredRequest[] = aliceDeliveries,
+): void {
+  const accepts = deliveries.filter(({ body }) =>
+    body.type === "Accept" && body.object?.id === follow.id?.href
+  );
+  strictEqual(accepts.length, 1, "Expected exactly one Accept for this Follow");
+  strictEqual(accepts[0].method, "POST");
+  strictEqual(accepts[0].body.actor, "https://relay.example.com/users/relay");
+  strictEqual(accepts[0].body.object.type, "Follow");
+  strictEqual(
+    accepts[0].body.object.actor?.id ?? accepts[0].body.object.actor,
+    follow.actorId?.href,
+  );
+}
+
 const nextFetch = globalThis.fetch;
 globalThis.fetch = (async (input: URL | RequestInfo, init?: RequestInit) => {
   const request = input instanceof Request ? input : new Request(input, init);
@@ -361,7 +380,10 @@ describe("LitePubRelay", () => {
     });
 
     const followActivity = new Follow({
-      id: new URL("https://remote.example.com/activities/follow/1"),
+      // Isolate delivery assertions from other tests and loop iterations.
+      id: new URL(
+        `https://remote.example.com/activities/follow/${crypto.randomUUID()}`,
+      ),
       actor: follower.id,
       object: new URL("https://relay.example.com/users/relay"),
     });
@@ -385,6 +407,7 @@ describe("LitePubRelay", () => {
     const deliveredActivities = recordInbox(daveInbox);
     const response = await relay.fetch(request);
     strictEqual(response.status, 202);
+    assertAcceptDelivered(followActivity, deliveredActivities);
 
     // Verify handler was called
     strictEqual(handlerCalled, true);
@@ -487,7 +510,10 @@ describe("LitePubRelay", () => {
 
     // Public follow activity
     const followActivity = new Follow({
-      id: new URL("https://remote.example.com/activities/follow/1"),
+      // Isolate delivery assertions from other tests and loop iterations.
+      id: new URL(
+        `https://remote.example.com/activities/follow/${crypto.randomUUID()}`,
+      ),
       actor: follower.id,
       object: new URL("https://www.w3.org/ns/activitystreams#Public"),
     });
@@ -510,6 +536,7 @@ describe("LitePubRelay", () => {
 
     const response = await relay.fetch(request);
     strictEqual(response.status, 202);
+    assertAcceptDelivered(followActivity);
 
     // Verify follower was stored with "pending" state
     const followerData = await kv.get([
@@ -594,7 +621,10 @@ describe("LitePubRelay", () => {
       strictEqual(await relay.getFollower(followerId), null);
 
       const followActivity = new Follow({
-        id: new URL("https://remote.example.com/activities/follow/1"),
+        // Isolate delivery assertions from other tests and loop iterations.
+        id: new URL(
+          `https://remote.example.com/activities/follow/${crypto.randomUUID()}`,
+        ),
         actor: new URL(followerId),
         object: new URL("https://relay.example.com/users/relay"),
       });
@@ -613,6 +643,7 @@ describe("LitePubRelay", () => {
 
       const response = await relay.fetch(request);
       strictEqual(response.status, 202);
+      assertAcceptDelivered(followActivity);
 
       strictEqual(handlerCallCount, 1);
       const follower = await relay.getFollower(followerId);

packages/relay/src/mastodon.test.ts

@@ -108,6 +108,25 @@ function recordInbox(inbox: string): DeliveredRequest[] {
   return recorded;
 }
 
+const aliceDeliveries = recordInbox(aliceInbox);
+
+function assertAcceptDelivered(
+  follow: Follow,
+  deliveries: readonly DeliveredRequest[] = aliceDeliveries,
+): void {
+  const accepts = deliveries.filter(({ body }) =>
+    body.type === "Accept" && body.object?.id === follow.id?.href
+  );
+  strictEqual(accepts.length, 1, "Expected exactly one Accept for this Follow");
+  strictEqual(accepts[0].method, "POST");
+  strictEqual(accepts[0].body.actor, "https://relay.example.com/users/relay");
+  strictEqual(accepts[0].body.object.type, "Follow");
+  strictEqual(
+    accepts[0].body.object.actor?.id ?? accepts[0].body.object.actor,
+    follow.actorId?.href,
+  );
+}
+
 const nextFetch = globalThis.fetch;
 globalThis.fetch = (async (input: URL | RequestInfo, init?: RequestInit) => {
   const request = input instanceof Request ? input : new Request(input, init);
@@ -406,7 +425,10 @@ describe("MastodonRelay", () => {
     });
 
     const followActivity = new Follow({
-      id: new URL("https://remote.example.com/activities/follow/1"),
+      // Isolate delivery assertions from other tests and loop iterations.
+      id: new URL(
+        `https://remote.example.com/activities/follow/${crypto.randomUUID()}`,
+      ),
       actor: follower.id,
       object: new URL("https://relay.example.com/users/relay"),
     });
@@ -429,6 +451,7 @@ describe("MastodonRelay", () => {
 
     const response = await relay.fetch(request);
     strictEqual(response.status, 202);
+    assertAcceptDelivered(followActivity);
 
     // Verify handler was called
     strictEqual(handlerCalled, true);
@@ -858,7 +881,10 @@ describe("MastodonRelay", () => {
 
     // Public follow activity
     const followActivity = new Follow({
-      id: new URL("https://remote.example.com/activities/follow/1"),
+      // Isolate delivery assertions from other tests and loop iterations.
+      id: new URL(
+        `https://remote.example.com/activities/follow/${crypto.randomUUID()}`,
+      ),
       actor: follower.id,
       object: new URL("https://www.w3.org/ns/activitystreams#Public"),
     });
@@ -881,6 +907,7 @@ describe("MastodonRelay", () => {
 
     const response = await relay.fetch(request);
     strictEqual(response.status, 202);
+    assertAcceptDelivered(followActivity);
 
     // Verify follower was stored
     const followerData = await kv.get([