Add JaCoCo test coverage configuration and CI reporting

.github/workflows/coverage.yml

@@ -0,0 +1,169 @@
+name: Test Coverage
+
+on:
+  pull_request:
+    branches: [ master ]
+
+permissions:
+  pull-requests: write
+  contents: read
+
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - name: Set up JDK 11
+        uses: actions/setup-java@v3
+        with:
+          java-version: '11'
+          distribution: 'temurin'
+
+      - name: Cache Gradle packages
+        uses: actions/cache@v3
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+          restore-keys: ${{ runner.os }}-gradle-
+
+      - name: Run tests and generate coverage report (PR branch)
+        run: ./gradlew test jacocoTestReport
+
+      - name: Save PR branch coverage report
+        run: cp build/reports/jacoco/test/jacocoTestReport.xml pr-coverage.xml
+
+      - name: Extract PR branch coverage percentage
+        id: pr_coverage
+        run: |
+          # Extract the report-level LINE counter (last occurrence in the XML)
+          line=$(grep -oP 'counter type="LINE" missed="\d+" covered="\d+"' pr-coverage.xml | tail -1)
+          missed=$(echo "$line" | grep -oP 'missed="\K\d+')
+          covered=$(echo "$line" | grep -oP 'covered="\K\d+')
+          total=$((missed + covered))
+          if [ "$total" -gt 0 ]; then
+            pct=$(awk "BEGIN {printf \"%.2f\", ($covered/$total)*100}")
+          else
+            pct="0.00"
+          fi
+          echo "coverage=$pct" >> "$GITHUB_OUTPUT"
+          echo "PR branch line coverage: $pct% (missed=$missed, covered=$covered)"
+
+      - name: Checkout base branch
+        run: git checkout ${{ github.base_ref }}
+
+      - name: Run tests and generate coverage report (base branch)
+        run: |
+          # Base branch may not have JaCoCo configured yet; skip gracefully
+          ./gradlew clean test jacocoTestReport || true
+
+      - name: Extract base branch coverage percentage
+        id: base_coverage
+        run: |
+          if [ -f build/reports/jacoco/test/jacocoTestReport.xml ]; then
+            line=$(grep -oP 'counter type="LINE" missed="\d+" covered="\d+"' build/reports/jacoco/test/jacocoTestReport.xml | tail -1)
+            missed=$(echo "$line" | grep -oP 'missed="\K\d+')
+            covered=$(echo "$line" | grep -oP 'covered="\K\d+')
+            total=$((missed + covered))
+            if [ "$total" -gt 0 ]; then
+              pct=$(awk "BEGIN {printf \"%.2f\", ($covered/$total)*100}")
+            else
+              pct="0.00"
+            fi
+            echo "coverage=$pct" >> "$GITHUB_OUTPUT"
+            echo "has_base=true" >> "$GITHUB_OUTPUT"
+            echo "Base branch line coverage: $pct% (missed=$missed, covered=$covered)"
+          else
+            echo "coverage=N/A" >> "$GITHUB_OUTPUT"
+            echo "has_base=false" >> "$GITHUB_OUTPUT"
+            echo "No JaCoCo report found on base branch"
+          fi
+
+      - name: Checkout PR branch again
+        run: git checkout ${{ github.event.pull_request.head.sha }}
+
+      - name: Restore PR coverage report
+        run: |
+          mkdir -p build/reports/jacoco/test
+          cp pr-coverage.xml build/reports/jacoco/test/jacocoTestReport.xml
+
+      - name: Post coverage comparison comment
+        uses: actions/github-script@v6
+        with:
+          script: |
+            const prCoverage = '${{ steps.pr_coverage.outputs.coverage }}';
+            const baseCoverage = '${{ steps.base_coverage.outputs.coverage }}';
+            const hasBase = '${{ steps.base_coverage.outputs.has_base }}' === 'true';
+
+            let diff = '';
+            let emoji = '';
+            if (hasBase && baseCoverage !== 'N/A') {
+              const delta = (parseFloat(prCoverage) - parseFloat(baseCoverage)).toFixed(2);
+              if (delta > 0) {
+                emoji = '🟢';
+                diff = `+${delta}%`;
+              } else if (delta < 0) {
+                emoji = '🔴';
+                diff = `${delta}%`;
+              } else {
+                emoji = '⚪';
+                diff = `±0.00%`;
+              }
+            }
+
+            let body = `## Test Coverage Report\n\n`;
+            body += `| Metric | Coverage |\n`;
+            body += `|--------|----------|\n`;
+            if (hasBase) {
+              body += `| **Base branch** (\`${{ github.base_ref }}\`) | ${baseCoverage}% |\n`;
+            } else {
+              body += `| **Base branch** (\`${{ github.base_ref }}\`) | _No JaCoCo configured_ |\n`;
+            }
+            body += `| **PR branch** (\`${{ github.head_ref }}\`) | ${prCoverage}% |\n`;
+            if (hasBase && baseCoverage !== 'N/A') {
+              body += `| **Diff** | ${emoji} ${diff} |\n`;
+            }
+
+            // Find and update existing comment or create new one
+            const marker = '<!-- coverage-report -->';
+            body = marker + '\n' + body;
+
+            const { data: comments } = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+            });
+
+            const existing = comments.find(c => c.body.includes(marker));
+            if (existing) {
+              await github.rest.issues.updateComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: existing.id,
+                body,
+              });
+            } else {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.issue.number,
+                body,
+              });
+            }
+
+      - name: Post per-file coverage details
+        uses: madrapps/jacoco-report@v1.6.1
+        with:
+          paths: build/reports/jacoco/test/jacocoTestReport.xml
+          token: ${{ secrets.GITHUB_TOKEN }}
+          min-coverage-overall: 34
+          min-coverage-changed-files: 60
+          title: "Per-File Coverage Details"
+          update-comment: true
+          pass-emoji: ':green_circle:'
+          fail-emoji: ':red_circle:'

build.gradle

@@ -4,6 +4,7 @@ plugins {
     id 'java'
     id "com.netflix.dgs.codegen" version "5.0.6"
     id "com.diffplug.spotless" version "6.2.1"
+    id 'jacoco'
 }
 
 version = '0.0.1-SNAPSHOT'
@@ -56,8 +57,39 @@ dependencies {
     testImplementation 'org.mybatis.spring.boot:mybatis-spring-boot-starter-test:2.2.2'
 }
 
+jacoco {
+    toolVersion = "0.8.8"
+}
+
+tasks.named('jacocoTestReport') {
+    dependsOn tasks.named('test')
+    reports {
+        xml.required = true
+        csv.required = false
+        html.required = true
+    }
+}
+
+tasks.named('jacocoTestCoverageVerification') {
+    violationRules {
+        rule {
+            limit {
+                counter = 'LINE'
+                value = 'COVEREDRATIO'
+                // TODO: raise this threshold over time as test coverage improves
+                minimum = 0.34
+            }
+        }
+    }
+}
+
 tasks.named('test') {
-	useJUnitPlatform()
+    useJUnitPlatform()
+    finalizedBy tasks.named('jacocoTestReport')
+}
+
+tasks.named('check') {
+    dependsOn tasks.named('jacocoTestCoverageVerification')
 }
 
 tasks.named('clean') {