@@ -55,7 +55,7 @@ public class NoDifficultyValidationTest {
     final BlockHeader parentHeader = mock(BlockHeader.class);
 
     final BlockHeader invalidHeader = mock(BlockHeader.class);
-    when(invalidHeader.getDifficulty()).thenReturn(Difficulty.MAX_VALUE);
+    when(invalidHeader.getDifficulty()).thenReturn(Difficulty.of(10));
     assertThat(rule.validate(invalidHeader, parentHeader, protocolContext)).isFalse();
 
     final BlockHeader validHeader = mock(BlockHeader.class);
/*
 * Copyright Hyperledger Besu Contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 */

package org.hyperledger.besu.consensus.merge.headervalidationrules;

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

import org.hyperledger.besu.consensus.merge.MergeContext;
import org.hyperledger.besu.ethereum.ProtocolContext;
import org.hyperledger.besu.ethereum.chain.MutableBlockchain;
import org.hyperledger.besu.ethereum.core.BlockHeader;
import org.hyperledger.besu.ethereum.core.Difficulty;

import java.util.Optional;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mock;
import org.mockito.junit.MockitoJUnitRunner;

@RunWith(MockitoJUnitRunner.class)
public class NoDifficultyValidationTest {

  @Mock private ProtocolContext protocolContext;
  @Mock private MutableBlockchain blockchain;
  @Mock private MergeContext mergeContext;

  @Before
  public void setUp() {
    when(blockchain.getTotalDifficultyByHash(any())).thenReturn(Optional.of(Difficulty.ONE));
    when(protocolContext.getBlockchain()).thenReturn(blockchain);
    when(mergeContext.getTerminalTotalDifficulty()).thenReturn(Difficulty.ONE);
    when(protocolContext.getConsensusContext(MergeContext.class)).thenReturn(mergeContext);
  }

  @Test
  public void difficultyMustBeZero() {
    final NoDifficultyRule rule = new NoDifficultyRule();
    final BlockHeader parentHeader = mock(BlockHeader.class);

    final BlockHeader invalidHeader = mock(BlockHeader.class);
    when(invalidHeader.getDifficulty()).thenReturn(Difficulty.MAX_VALUE);
    assertThat(rule.validate(invalidHeader, parentHeader, protocolContext)).isFalse();

    final BlockHeader validHeader = mock(BlockHeader.class);
    when(validHeader.getDifficulty()).thenReturn(Difficulty.ZERO);

    assertThat(rule.validate(validHeader, parentHeader, protocolContext)).isTrue();
  }
}

turns our Difficulty will overflow