fix: handle opaque attachment references

loadtest/im-pressure/dbverify_test.go

@@ -0,0 +1,24 @@
+package main
+
+import "testing"
+
+func TestExpectedDBMessagesIncludesObservedWithoutAck(t *testing.T) {
+	ledgers := map[string][]AcceptedMessage{
+		"a": {{RunID: "run-1", ClientMid: "acked", Topic: "grp-one", Seq: 1}},
+	}
+	observed := map[string][]AcceptedMessage{
+		"a": {
+			{RunID: "run-1", ClientMid: "unacked", Topic: "grp-one", Seq: 2},
+			{RunID: "other", ClientMid: "foreign", Topic: "grp-one", Seq: 3},
+		},
+		"b": {{RunID: "run-1", ClientMid: "unacked", Topic: "grp-one", Seq: 2}},
+	}
+
+	expected := expectedDBMessages("run-1", ledgers, observed)
+	if len(expected) != 2 {
+		t.Fatalf("expected messages=%d want=2: %+v", len(expected), expected)
+	}
+	if expected["acked"].Seq != 1 || expected["unacked"].Seq != 2 {
+		t.Fatalf("unexpected merged messages: %+v", expected)
+	}
+}