From 40262ce74932518344e6eb4a1e42ae51af79ef81 Mon Sep 17 00:00:00 2001
From: "Andrei G." <k05h31@gmail.com>
Date: Thu, 19 Mar 2026 18:35:53 +0100
Subject: [PATCH] ci(nextest): partition unit tests into 4 parallel shards

Add ci-partition profile to nextest.toml for hash-based test partitioning.
Replace sequential test job with 4-way matrix, reducing test time by ~70%.

Each shard runs --partition hash:K/4 independently:
- Shard 1/4, 2/4, 3/4, 4/4 run in parallel (~3min each vs 10min total)
- Build job (25min) remains pipeline bottleneck
- No changes to integration tests or coverage jobs
- JUnit reports collected from each shard

Fixes: improves CI pipeline parallelism
---
 .github/nextest.toml     |  8 ++++++++
 .github/workflows/ci.yml | 18 ++++++++++++------
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/.github/nextest.toml b/.github/nextest.toml
index 8338630f..df048612 100644
--- a/.github/nextest.toml
+++ b/.github/nextest.toml
@@ -18,3 +18,11 @@ test-threads = 8
 [profile.ci.junit]
 # Store JUnit XML report for CI
 path = "target/nextest/ci/junit.xml"
+
+[profile.ci-partition]
+# Used by the partitioned test matrix in CI (unit tests only).
+# Each shard receives --partition hash:K/4 on the command line.
+test-threads = 8
+
+[profile.ci-partition.junit]
+path = "target/nextest/ci/junit.xml"
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 9f5b0f55..cfc36d13 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -187,24 +187,30 @@ jobs:
           retention-days: 1
 
   test:
-    name: Test (${{ matrix.os }})
+    name: "Test (shard ${{ matrix.partition }})"
     needs: [detect-changes, lint-fmt, lint-clippy, build-tests]
     if: needs.detect-changes.outputs.run-full-ci == 'true'
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
     timeout-minutes: 10
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest]
+        partition: ["1/4", "2/4", "3/4", "4/4"]
     steps:
       - uses: actions/checkout@v6
       - uses: taiki-e/install-action@9786bf093d06fe2c715bc12b6ff3b97a491cab4f # nextest
       - name: Download test archive
         uses: actions/download-artifact@v7
         with:
-          name: nextest-archive-${{ matrix.os }}
-      - name: Run tests
-        run: cargo nextest run --config-file .github/nextest.toml --archive-file nextest-archive.tar.zst --workspace-remap .
+          name: nextest-archive-ubuntu-latest
+      - name: "Run tests (shard ${{ matrix.partition }})"
+        run: |
+          cargo nextest run \
+            --config-file .github/nextest.toml \
+            --archive-file nextest-archive.tar.zst \
+            --workspace-remap . \
+            --profile ci-partition \
+            --partition hash:${{ matrix.partition }}
 
   integration:
     name: Integration Tests