@Override
        public boolean equals(Object o) {
            if (this == o) return true;
            if (o == null || getClass() != o.getClass()) return false;
            MockOffsetMetadata that = (MockOffsetMetadata) o;
            return id == that.id;
        }
Reopening the log causes all unflushed data to be lost.
raft/src/test/java/org/apache/kafka/raft/MockLog.java