Add regression test for matrix-org/synapse#1563

Currently fails on Synapse.

tests/federation_room_ban_test.go

@@ -0,0 +1,44 @@
+package tests
+
+import (
+	"testing"
+
+	"github.com/matrix-org/complement/internal/b"
+	"github.com/matrix-org/complement/internal/client"
+)
+
+// Regression test for https://github.com/matrix-org/synapse/issues/1563
+// Create a federation room. Bob bans Alice. Bob unbans Alice. Bob invites Alice (unbanning her). Ensure the invite is
+// received and can be accepted.
+func TestUnbanViaInvite(t *testing.T) {
+	deployment := Deploy(t, b.BlueprintFederationOneToOneRoom)
+	defer deployment.Destroy(t)
+
+	alice := deployment.Client(t, "hs1", "@alice:hs1")
+	bob := deployment.Client(t, "hs2", "@bob:hs2")
+
+	roomID := bob.CreateRoom(t, map[string]interface{}{
+		"preset": "public_chat",
+	})
+	alice.JoinRoom(t, roomID, []string{"hs2"})
+
+	// Ban Alice
+	bob.MustDoFunc(t, "POST", []string{"_matrix", "client", "r0", "rooms", roomID, "ban"}, client.WithJSONBody(t, map[string]interface{}{
+		"user_id": alice.UserID,
+	}))
+	alice.MustSyncUntil(t, client.SyncReq{}, client.SyncLeftFrom(alice.UserID, roomID))
+
+	// Unban Alice
+	bob.MustDoFunc(t, "POST", []string{"_matrix", "client", "r0", "rooms", roomID, "unban"}, client.WithJSONBody(t, map[string]interface{}{
+		"user_id": alice.UserID,
+	}))
+	bob.MustSyncUntil(t, client.SyncReq{}, client.SyncLeftFrom(alice.UserID, roomID))
+
+	// Re-invite Alice
+	bob.InviteRoom(t, roomID, alice.UserID)
+	bob.MustSyncUntil(t, client.SyncReq{}, client.SyncInvitedTo(alice.UserID, roomID))
+	alice.MustSyncUntil(t, client.SyncReq{}, client.SyncInvitedTo(alice.UserID, roomID))
+
+	// Alice accepts (this is what previously failed in the issue)
+	alice.JoinRoom(t, roomID, []string{"hs2"})
+}