Add PivotUpdator tests (#6399)

* Add PivotUpdater tests, cosmetic rename

* whitespaces

* revert class name change

src/Nethermind/Nethermind.Merge.Plugin.Test/Synchronization/PivotUpdatorTests.cs

@@ -0,0 +1,95 @@
+// SPDX-FileCopyrightText: 2022 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using FluentAssertions;
+using NUnit.Framework;
+using NSubstitute;
+using Nethermind.Blockchain;
+using Nethermind.Blockchain.Synchronization;
+using Nethermind.Config;
+using Nethermind.Core;
+using Nethermind.Core.Crypto;
+using Nethermind.Core.Test.Builders;
+using Nethermind.Db;
+using Nethermind.Logging;
+using Nethermind.Merge.Plugin.Handlers;
+using Nethermind.Merge.Plugin.Synchronization;
+using Nethermind.Serialization.Rlp;
+using Nethermind.Specs;
+using Nethermind.Specs.Forks;
+using Nethermind.Stats.Model;
+using Nethermind.Synchronization;
+using Nethermind.Synchronization.ParallelSync;
+using Nethermind.Synchronization.Peers;
+
+namespace Nethermind.Merge.Plugin.Test.Synchronization
+{
+    public class PivotUpdatorTests
+    {
+        private IBlockTree? _blockTree;
+        private ISyncModeSelector? _syncModeSelector;
+        private ISyncPeerPool? _syncPeerPool;
+        private ISyncConfig? _syncConfig;
+        private IBlockCacheService? _blockCacheService;
+        private IBeaconSyncStrategy? _beaconSyncStrategy;
+        private IDb? _metadataDb;
+        private IBlockTree? _externalPeerBlockTree;
+
+        [SetUp]
+        public void Setup()
+        {
+            Block genesisBlock = Build.A.Block.WithNumber(0).TestObject;
+            TestSpecProvider specProvider = new(Cancun.Instance);
+            specProvider.TerminalTotalDifficulty = 0;
+            _externalPeerBlockTree = Build.A.BlockTree(genesisBlock, specProvider)
+                .WithoutSettingHead
+                .OfChainLength(20)
+                .TestObject;
+
+            ISyncPeer? fakePeer = Substitute.For<ISyncPeer>();
+            fakePeer.GetHeadBlockHeader(default, default).ReturnsForAnyArgs(x => _externalPeerBlockTree!.Head!.Header);
+            NetworkNode node = new(TestItem.PublicKeyA, "127.0.0.1", 30303, 100L);
+            fakePeer.Node.Returns(new Node(node));
+
+            _syncPeerPool = Substitute.For<ISyncPeerPool>();
+            _syncPeerPool.InitializedPeers.Returns(new[] { new PeerInfo(fakePeer) });
+
+            _blockTree = Substitute.For<IBlockTree>();
+            _syncModeSelector = Substitute.For<ISyncModeSelector>();
+            _syncConfig = Substitute.For<ISyncConfig>();
+            _blockCacheService = new BlockCacheService();
+            _beaconSyncStrategy = Substitute.For<IBeaconSyncStrategy>();
+            _metadataDb = new MemDb();
+
+            PivotUpdator pivotUpdator = new(
+              _blockTree,
+              _syncModeSelector,
+              _syncPeerPool,
+              _syncConfig,
+              _blockCacheService,
+              _beaconSyncStrategy,
+              _metadataDb,
+              LimboLogs.Instance
+            );
+        }
+
+        [Test]
+        public void TrySetFreshPivot_SavesFinalizedHashInDb()
+        {
+            SyncModeChangedEventArgs args = new(SyncMode.FastSync, SyncMode.UpdatingPivot);
+            Hash256 expectedFinalizedHash = _externalPeerBlockTree!.HeadHash;
+            long expectedPivotBlockNumber = _externalPeerBlockTree!.Head!.Number;
+            _beaconSyncStrategy!.GetFinalizedHash().Returns(expectedFinalizedHash);
+
+            _syncModeSelector!.Changed += Raise.EventWith(args);
+
+            byte[] storedData = _metadataDb!.Get(MetadataDbKeys.UpdatedPivotData)!;
+            RlpStream pivotStream = new(storedData!);
+            long storedPivotBlockNumber = pivotStream.DecodeLong();
+            Hash256 storedFinalizedHash = pivotStream.DecodeKeccak()!;
+
+            storedFinalizedHash.Should().Be(expectedFinalizedHash);
+            expectedPivotBlockNumber.Should().Be(storedPivotBlockNumber);
+        }
+    }
+}