Testing workflow (#3002)

* Run test for only changed exercises

Author: jagdish-15

.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()

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