Test project tests to be split in chunks and run in parallel

.github/workflows/nethermind-tests.yml

@@ -23,7 +23,7 @@ env:
 
 jobs:
   tests:
-    name: Run ${{ matrix.project }}
+    name: Run ${{ matrix.project }}${{ matrix.chunk && format(' ({0})', matrix.chunk) || '' }}
     runs-on: ubuntu-latest
     continue-on-error: true
     outputs:
@@ -40,7 +40,6 @@ jobs:
           - Ethereum.KeyAddress.Test
           - Ethereum.KeyStore.Test
           - Ethereum.Legacy.Blockchain.Block.Test
-          - Ethereum.Legacy.Blockchain.Test
           - Ethereum.Legacy.Transition.Test
           - Ethereum.Legacy.VM.Test
           - Ethereum.PoW.Test
@@ -91,6 +90,16 @@ jobs:
           - Nethermind.TxPool.Test
           - Nethermind.Wallet.Test
           - Nethermind.Xdc.Test
+        chunk: ['']
+        include:
+          - project: Ethereum.Legacy.Blockchain.Test
+            chunk: 1of4
+          - project: Ethereum.Legacy.Blockchain.Test
+            chunk: 2of4
+          - project: Ethereum.Legacy.Blockchain.Test
+            chunk: 3of4
+          - project: Ethereum.Legacy.Blockchain.Test
+            chunk: 4of4
     steps:
       - name: Check out repository
         uses: actions/checkout@v6
@@ -103,6 +112,8 @@ jobs:
       - name: ${{ matrix.project }}
         id: test
         working-directory: src/Nethermind/${{ matrix.project }}
+        env:
+          TEST_CHUNK: ${{ matrix.chunk }}
         run: |
           dotnet test --project ${{ matrix.project }}.csproj -c release \
             ${{ env.COLLECT_COVERAGE == 'true' && '--coverage --coverage-output-format cobertura --coverage-settings $GITHUB_WORKSPACE/src/Nethermind/codecoverage.config' || '' }}
@@ -115,15 +126,15 @@ jobs:
         if: success() || failure()
         uses: actions/upload-artifact@v4
         with:
-          name: ${{ matrix.project }}-outcome
+          name: ${{ matrix.project }}${{ matrix.chunk && format('-{0}', matrix.chunk) || '' }}-outcome
           path: test.outcome
           retention-days: 1
 
       - name: Upload coverage report
         if: env.COLLECT_COVERAGE == 'true'
         uses: actions/upload-artifact@v4
         with:
-          name: ${{ matrix.project }}-coverage
+          name: ${{ matrix.project }}${{ matrix.chunk && format('-{0}', matrix.chunk) || '' }}-coverage
           path: src/Nethermind/artifacts/bin/${{ matrix.project }}/release/TestResults/*.cobertura.xml
           retention-days: 1
 

src/Nethermind/Ethereum.Test.Base/TestChunkFilter.cs

@@ -0,0 +1,60 @@
+// SPDX-FileCopyrightText: 2025 Demerzel Solutions Limited
+// SPDX-License-Identifier: LGPL-3.0-only
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Ethereum.Test.Base;
+
+/// <summary>
+/// Filters tests into chunks for parallel CI execution.
+/// Set TEST_CHUNK environment variable to "1of3", "2of3", "3of3" etc.
+/// Partitions tests by index for consistent and even distribution.
+/// </summary>
+public static class TestChunkFilter
+{
+    public static IEnumerable<T> FilterByChunk<T>(IEnumerable<T> tests)
+    {
+        (int Index, int Total)? chunkConfig = GetChunkConfig();
+
+        if (chunkConfig is null)
+        {
+            return tests;
+        }
+
+        ICollection<T> testList = tests as ICollection<T> ?? [.. tests];
+        (int chunkIndex, int totalChunks) = chunkConfig.Value;
+
+        int count = testList.Count;
+        int chunkSize = count / totalChunks;
+        int remainder = count % totalChunks;
+
+        int skip = (chunkIndex - 1) * chunkSize;
+        int take = chunkSize + (chunkIndex == totalChunks ? remainder : 0);
+
+        return testList.Skip(skip).Take(take);
+
+        static (int Index, int Total)? GetChunkConfig()
+        {
+            string? chunkEnv = Environment.GetEnvironmentVariable("TEST_CHUNK");
+
+            if (string.IsNullOrEmpty(chunkEnv))
+            {
+                return null;
+            }
+
+            string[] parts = chunkEnv.Split("of", StringSplitOptions.None);
+
+            if (parts.Length != 2 ||
+                !int.TryParse(parts[0], out int index) ||
+                !int.TryParse(parts[1], out int total) ||
+                index < 1 || index > total || total < 1)
+            {
+                throw new ArgumentException($"Invalid TEST_CHUNK format: '{chunkEnv}'. Expected format: '1of3', '2of5', etc.");
+            }
+
+            return (index, total);
+        }
+    }
+}

src/Nethermind/Ethereum.Test.Base/TestsSourceLoader.cs

@@ -24,12 +24,15 @@ public TestsSourceLoader(ITestLoadStrategy testLoadStrategy, string path, string
 
         public IEnumerable<EthereumTest> LoadTests()
         {
-            return _testLoadStrategy.Load(_path, _wildcard);
+            IEnumerable<EthereumTest> tests = _testLoadStrategy.Load(_path, _wildcard);
+            return TestChunkFilter.FilterByChunk(tests);
         }
+
         public IEnumerable<TTestType> LoadTests<TTestType>()
             where TTestType : EthereumTest
         {
-            return _testLoadStrategy.Load(_path, _wildcard).Cast<TTestType>();
+            IEnumerable<TTestType> tests = _testLoadStrategy.Load(_path, _wildcard).Cast<TTestType>();
+            return TestChunkFilter.FilterByChunk(tests);
         }
     }
 }