ci: add JaCoCo code coverage reporting workflow

- Uses JaCoCo 0.8.12 agent to instrument tests and collect coverage data
- Generates HTML, XML, and CSV coverage reports
- Publishes coverage summary in GitHub Actions step summary
- Uploads coverage report as build artifact (30-day retention)
- Includes optional Codecov upload for external tracking
- Runs on JDK 17, covers all test suites including CommunityDetectorTest
- Added coverage badge to README

Author: sauravbhattacharya001

.github/workflows/coverage.yml

@@ -0,0 +1,117 @@
+name: Code Coverage
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+
+permissions:
+  contents: read
+
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          java-version: 17
+          distribution: temurin
+
+      - name: Download test dependencies
+        run: |
+          mkdir -p Gvisual/lib/test
+          # JUnit 4 + Hamcrest
+          curl -sL -o Gvisual/lib/test/junit-4.13.2.jar \
+            https://repo1.maven.org/maven2/junit/junit/4.13.2/junit-4.13.2.jar
+          curl -sL -o Gvisual/lib/test/hamcrest-core-1.3.jar \
+            https://repo1.maven.org/maven2/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar
+          # JaCoCo agent + CLI for coverage instrumentation and reporting
+          curl -sL -o /tmp/jacoco.zip \
+            https://repo1.maven.org/maven2/org/jacoco/jacoco/0.8.12/jacoco-0.8.12.zip
+          unzip -o /tmp/jacoco.zip -d /tmp/jacoco
+          cp /tmp/jacoco/lib/jacocoagent.jar Gvisual/lib/test/jacocoagent.jar
+          cp /tmp/jacoco/lib/jacococli.jar Gvisual/lib/test/jacococli.jar
+
+      - name: Compile source
+        working-directory: Gvisual
+        run: |
+          mkdir -p build/classes
+          find src -name '*.java' > sources.txt
+          javac -source 8 -target 8 \
+            -cp "$(find lib -name '*.jar' -not -path 'lib/test/*' | tr '\n' ':')" \
+            -d build/classes \
+            @sources.txt
+
+      - name: Compile tests
+        working-directory: Gvisual
+        run: |
+          mkdir -p build/test/classes
+          find test -name '*.java' > test-sources.txt
+          javac -source 8 -target 8 \
+            -cp "build/classes:$(find lib -name '*.jar' | tr '\n' ':')" \
+            -d build/test/classes \
+            @test-sources.txt
+
+      - name: Run tests with JaCoCo coverage
+        working-directory: Gvisual
+        run: |
+          java \
+            -javaagent:lib/test/jacocoagent.jar=destfile=build/jacoco.exec,includes=gvisual.*:app.* \
+            -cp "build/classes:build/test/classes:$(find lib -name '*.jar' | tr '\n' ':')" \
+            org.junit.runner.JUnitCore \
+            app.UtilMethodsTest \
+            gvisual.EdgeTest \
+            gvisual.GraphStatsTest \
+            gvisual.ShortestPathFinderTest \
+            gvisual.CommunityDetectorTest
+
+      - name: Generate coverage report
+        working-directory: Gvisual
+        run: |
+          mkdir -p build/coverage
+          # Generate HTML report
+          java -jar lib/test/jacococli.jar report build/jacoco.exec \
+            --classfiles build/classes \
+            --sourcefiles src \
+            --html build/coverage/html \
+            --xml build/coverage/coverage.xml \
+            --csv build/coverage/coverage.csv \
+            --name "GraphVisual Coverage Report"
+
+      - name: Coverage summary
+        working-directory: Gvisual
+        run: |
+          echo "## 📊 Code Coverage Report" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          # Parse CSV for summary (skip header, sum instruction covered/missed)
+          if [ -f build/coverage/coverage.csv ]; then
+            echo "| Package | Class | Instruction Coverage |" >> $GITHUB_STEP_SUMMARY
+            echo "|---------|-------|---------------------|" >> $GITHUB_STEP_SUMMARY
+            tail -n +2 build/coverage/coverage.csv | while IFS=',' read -r group package class inst_missed inst_covered branch_missed branch_covered line_missed line_covered complexity_missed complexity_covered method_missed method_covered; do
+              total=$((inst_missed + inst_covered))
+              if [ "$total" -gt 0 ]; then
+                pct=$((inst_covered * 100 / total))
+                echo "| $package | $class | ${pct}% (${inst_covered}/${total}) |" >> $GITHUB_STEP_SUMMARY
+              fi
+            done
+          fi
+
+      - name: Upload coverage report
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-report
+          path: Gvisual/build/coverage/
+          retention-days: 30
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          files: Gvisual/build/coverage/coverage.xml
+          fail_ci_if_error: false
+        continue-on-error: true

README.md

@@ -12,6 +12,7 @@ Built with Java and [JUNG](http://jung.sourceforge.net/) (Java Universal Network
 [![JUNG](https://img.shields.io/badge/JUNG-2.0.1-blue)](http://jung.sourceforge.net/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://github.com/sauravbhattacharya001/GraphVisual/blob/master/LICENSE)
 [![Docker](https://github.com/sauravbhattacharya001/GraphVisual/actions/workflows/docker.yml/badge.svg)](https://github.com/sauravbhattacharya001/GraphVisual/actions/workflows/docker.yml)
+[![Coverage](https://github.com/sauravbhattacharya001/GraphVisual/actions/workflows/coverage.yml/badge.svg)](https://github.com/sauravbhattacharya001/GraphVisual/actions/workflows/coverage.yml)
 [![GitHub repo size](https://img.shields.io/github/repo-size/sauravbhattacharya001/GraphVisual)](https://github.com/sauravbhattacharya001/GraphVisual)
 
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