From 6276d3b8fc1c5a5cc7da27b077166cbfe8aed26b Mon Sep 17 00:00:00 2001
From: Jagdish Prajapati <jagadishdrp@gmail.com>
Date: Fri, 5 Sep 2025 16:10:52 +0530
Subject: [PATCH 1/3] Run test for only changed exercises

---
 .github/workflows/java.yml | 20 ++++++++++++++++-
 bin/test-changed-exercise  | 44 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+), 1 deletion(-)
 create mode 100644 bin/test-changed-exercise

diff --git a/.github/workflows/java.yml b/.github/workflows/java.yml
index 48fc8795a..a966405ee 100644
--- a/.github/workflows/java.yml
+++ b/.github/workflows/java.yml
@@ -39,8 +39,9 @@ jobs:
         run: ./gradlew check --exclude-task test --continue
         working-directory: exercises
 
-  test:
+  test-all:
     name: Test all exercises using java-test-runner
+    if: github.event_name == 'push' || github.event_name == 'workflow_dispatch'
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
@@ -52,3 +53,20 @@ jobs:
           name: test-results
           path: exercises/**/build/results.json
         if: failure()
+        
+  test-changed:
+    name: Test changed exercises using java-test-runner
+    if: github.event_name == 'pull_request'
+    runs-on: ubuntu-24.04
+    steps:
+      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8
+        with:
+          fetch-depth: 0
+      - name: Test changed exercises using java-test-runner
+        run: bin/test-changed-exercise
+      - name: Archive test results
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02
+        with:
+          name: test-results
+          path: exercises/**/build/results.json
+        if: failure()
diff --git a/bin/test-changed-exercise b/bin/test-changed-exercise
new file mode 100644
index 000000000..d930478f6
--- /dev/null
+++ b/bin/test-changed-exercise
@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+set -eo pipefail
+
+# Determine the base branch of the PR
+BASE_BRANCH=${GITHUB_BASE_REF:-main}
+
+# Fetch full history for proper diff
+git fetch origin "$BASE_BRANCH"
+
+# Compute merge base
+MERGE_BASE=$(git merge-base HEAD origin/$BASE_BRANCH)
+
+# Get changed files relative to merge base
+changed_files=$(git diff --name-only "$MERGE_BASE" HEAD)
+
+# Extract unique exercise directories
+changed_exercises=$(echo "$changed_files" | \
+  grep -E '^exercises/(practice|concept)/[^/]+/.+\.(java|gradle)$' | \
+  cut -d/ -f1-3 | sort -u)
+
+if [ -z "$changed_exercises" ]; then
+  echo "No relevant exercises changed, skipping tests."
+  exit 0
+fi
+
+# Print exercises
+echo "Changed exercises detected:"
+echo "$changed_exercises"
+echo "----------------------------------------"
+
+# Run tests
+for dir in $changed_exercises; do
+  slug=$(basename "$dir")
+
+  echo "========================================"
+  echo "=== Running tests for $slug ==="
+  echo "========================================"
+
+  if [[ $dir == exercises/practice/* ]]; then
+    ./exercises/gradlew -p exercises ":practice:$slug:test"
+  elif [[ $dir == exercises/concept/* ]]; then
+    ./exercises/gradlew -p exercises ":concept:$slug:test"
+  fi
+done

From f897273692e8c632865da385eb9292f77987d4a4 Mon Sep 17 00:00:00 2001
From: Jagdish Prajapati <jagadishdrp@gmail.com>
Date: Fri, 5 Sep 2025 16:18:29 +0530
Subject: [PATCH 2/3] Make test-changed-exercise executable

---
 bin/test-changed-exercise | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 mode change 100644 => 100755 bin/test-changed-exercise

diff --git a/bin/test-changed-exercise b/bin/test-changed-exercise
old mode 100644
new mode 100755

From 3afd338f36e90c1095c0b1b7c1a1708b54f1f623 Mon Sep 17 00:00:00 2001
From: Jagdish Prajapati <jagadishdrp@gmail.com>
Date: Sat, 6 Sep 2025 22:25:20 +0530
Subject: [PATCH 3/3] Update bin/test-changed-exercise

Co-authored-by: Kah Goh <villastar@yahoo.com.au>
---
 bin/test-changed-exercise | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bin/test-changed-exercise b/bin/test-changed-exercise
index d930478f6..776e940e1 100755
--- a/bin/test-changed-exercise
+++ b/bin/test-changed-exercise
@@ -8,7 +8,7 @@ BASE_BRANCH=${GITHUB_BASE_REF:-main}
 git fetch origin "$BASE_BRANCH"
 
 # Compute merge base
-MERGE_BASE=$(git merge-base HEAD origin/$BASE_BRANCH)
+MERGE_BASE=$(git merge-base HEAD origin/"$BASE_BRANCH")
 
 # Get changed files relative to merge base
 changed_files=$(git diff --name-only "$MERGE_BASE" HEAD)