diff --git a/app/frontend/src/mocks/mogaco.ts b/app/frontend/src/mocks/mogaco.ts
index b1846c35f..8803ac0aa 100644
--- a/app/frontend/src/mocks/mogaco.ts
+++ b/app/frontend/src/mocks/mogaco.ts
@@ -67,6 +67,23 @@ export const mogacoAPIHandlers = [
   http.get('/mogaco/:id/participants', ({ params: { id } }) =>
     HttpResponse.json<Participant[]>(participantsList[Number(id) - 1]),
   ),
-  http.post('mogaco/:id/join', () => {}),
-  http.delete('mogaco/:id/join', () => {}),
+  http.post<{ id: string }, { memberId: string }>(
+    'mogaco/:id/join',
+    async ({ request, params: { id } }) => {
+      const { memberId } = await request.json();
+      participantsList[Number(id) - 1] = [
+        ...participantsList[Number(id) - 1],
+        userList[Number(memberId) - 1],
+      ];
+    },
+  ),
+  http.delete<{ id: string }, { memberId: string }>(
+    'mogaco/:id/join',
+    async ({ request, params: { id } }) => {
+      const { memberId } = await request.json();
+      participantsList[Number(id) - 1] = participantsList[
+        Number(id) - 1
+      ].filter((participant) => participant.id !== memberId);
+    },
+  ),
 ];