resolver: the refused-query test asks several operators, one query each (closes #251)

The test asked one operator's recursive resolver for eight record types
at each of its two addresses, and passed only when all eight were
refused within one attempt; when that operator stopped answering, next
went red. It is now TestQueryServers_RecursiveResolverRefused: through
the existing QueryServers test export it sends one A query to public
resolvers of four operators in turn, inside livednstest.Retry, moving
on when one gives no reply. Each refuses a query not asking for
recursion and answers one that does, so putting the resend asking for
recursion back still fails the test at once.

Model: opus-5-5

TODO.md

@@ -19,6 +19,8 @@ trial run of the finished image: https://git.eeqj.de/sneak/dnswatcher/issues/149
 
 # Completed Steps
 
+- 2026-10-02: the refused-query test sends one query to four operators' public
+  resolvers in turn until one replies, not eight to one operator (closes #251).
 - 2026-10-02: a name removed from `DNSWATCHER_TARGETS` leaves the state, and so
   the dashboard and API, at startup, before the first check (closes #223).
 - 2026-10-02: a record type whose query to a nameserver fails keeps its previous

internal/resolver/resolver_test.go

@@ -442,48 +442,45 @@ func TestQueryNameserver_Refused(t *testing.T) {
 	assert.Equal(t, "server returned REFUSED", resp.Error)
 }
 
-// TestQueryNameserverIP_RecursiveResolverRefused asks Quad9, a public
-// recursive resolver, about google.com at both of its addresses. Quad9
-// refuses a query that does not ask for recursion and answers one that
-// does. The resolver never asks for recursion, so it must be reported
-// as refusing, never as answering.
-func TestQueryNameserverIP_RecursiveResolverRefused(t *testing.T) {
+// TestQueryServers_RecursiveResolverRefused passes a public recursive
+// resolver to QueryServers as the server of google.com. These resolvers
+// refuse a query that does not ask for recursion and answer one that
+// does. The resolver never asks for recursion, so the query must be
+// reported as refused, never answered. Each resolver is run by a
+// different operator, and they are asked in turn until one replies, so
+// one operator not answering does not fail the test.
+func TestQueryServers_RecursiveResolverRefused(t *testing.T) {
 	t.Parallel()
 
 	r := newTestResolver(t)
+	resolvers := []string{
+		"64.6.64.6", "185.222.222.222", "4.2.2.1", "9.9.9.9",
+	}
 
-	for _, ip := range []string{"9.9.9.9", "149.112.112.112"} {
-		var resp *resolver.NameserverResponse
+	var err error
 
 	livednstest.Retry(
 		t,
-			"QueryNameserverIP("+ip+", google.com)",
+		"QueryServers(public recursive resolvers, google.com)",
 		func(ctx context.Context) error {
-				var err error
-
-				resp, err = r.QueryNameserverIP(
-					ctx, ip, ip, "google.com",
+			for _, ip := range resolvers {
+				_, err = r.QueryServers(
+					ctx, []string{ip}, "google.com.", "google.com.",
+					dns.TypeA,
 				)
-				if err != nil {
-					return err
-				}
-
-				// A timeout or a network error is no reply at all.
-				if resp.Status == resolver.StatusTimeout ||
-					strings.HasPrefix(resp.Error, "network error") {
-					return fmt.Errorf(
-						"%w: %s: %s",
-						livednstest.ErrNoAnswer, ip, resp.Error,
-					)
-				}
 
+				// A refusal or an answer is a reply; anything else may
+				// be no reply at all, so the next resolver is asked.
+				if err == nil || errors.Is(err, resolver.ErrRefused) {
 					return nil
+				}
+			}
+
+			return fmt.Errorf("%w: %w", livednstest.ErrNoAnswer, err)
 		},
 	)
 
-		assert.Equal(t, resolver.StatusError, resp.Status, ip)
-		assert.Equal(t, "server returned REFUSED", resp.Error, ip)
-	}
+	require.ErrorIs(t, err, resolver.ErrRefused)
 }
 
 // googleNameserverIPv4s returns the IPv4 addresses of google.com's