add ci for running unit tests using github action

Author: cuongrep

.github/workflows/QUICK_START.md

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+# GitHub Actions Quick Start
+
+Get automated testing running in **30 seconds**! No signup required.
+
+## ⚡ 30-Second Setup
+
+```bash
+# Your workflow is already configured!
+# Just push to GitHub:
+
+git add .github/workflows/ci.yml
+git commit -m "Add GitHub Actions CI"
+git push origin main
+```
+
+**That's it!** Go to your repository → **Actions** tab to watch it run.
+
+## What Just Happened?
+
+GitHub Actions will now automatically:
+
+1. ✅ **Run on every push** to any branch
+2. ✅ **Run on every pull request**
+3. ✅ **Test your code** (all 46 tests)
+4. ✅ **Report results** in PR comments
+5. ✅ **Cache dependencies** for faster builds
+
+## First Build
+
+### Expected Timeline
+
+```
+0:00 - Checkout code           (5 seconds)
+0:05 - Set up Java 17           (10 seconds)
+0:15 - Download dependencies    (2-3 minutes) ⏱️
+3:00 - Run tests                (30 seconds)
+3:30 - Upload reports           (10 seconds)
+✅ Done!                        (~4 minutes total)
+```
+
+### Next Builds (With Cache)
+
+```
+0:00 - Checkout code           (5 seconds)
+0:05 - Set up Java 17           (10 seconds)
+0:15 - Restore cache            (30 seconds) ⚡
+0:45 - Run tests                (30 seconds)
+1:15 - Upload reports           (10 seconds)
+✅ Done!                        (~1.5 minutes total)
+```
+
+## Viewing Your Build
+
+### In the Actions Tab
+
+1. Go to your GitHub repository
+2. Click **Actions** tab (top menu)
+3. See your workflow runs
+
+### In Pull Requests
+
+Test results appear automatically in PR comments:
+
+```
+✅ All checks have passed
+• test — 46 tests passed
+• integration-test — 15 tests passed
+• build — Build successful
+```
+
+## Understanding the Workflow
+
+### What Runs When
+
+```
+Every push/PR:
+├─ test job
+│  └─ Runs all 46 tests
+│
+├─ integration-test job
+│  └─ Runs repository tests
+│
+└─ build job (main/develop only)
+   └─ Builds JAR file
+```
+
+### Jobs Run in Parallel
+
+```
+    test (1-2 min)
+         ↓
+    integration-test (1-2 min)
+         ↓
+    build (30 sec) ← Only on main/develop
+```
+
+## Adding a Status Badge
+
+Show your build status in README.md:
+
+```markdown
+![CI](https://github.com/YOUR_USERNAME/LibraryManagementAPI/workflows/CI/badge.svg)
+```
+
+Replace `YOUR_USERNAME` with your GitHub username.
+
+**Result:**
+
+![CI](https://github.com/username/repo/workflows/CI/badge.svg) ← Shows build status
+
+## Common Scenarios
+
+### Scenario 1: Push to Feature Branch
+
+```bash
+git checkout -b feature/new-feature
+git commit -m "Add new feature"
+git push origin feature/new-feature
+```
+
+**What happens:**
+- ✅ Tests run automatically
+- ✅ Results shown in GitHub
+- ❌ Build job DOES NOT run (not main/develop)
+
+### Scenario 2: Create Pull Request
+
+```bash
+# Create PR on GitHub
+```
+
+**What happens:**
+- ✅ Tests run on PR
+- ✅ Results posted as PR comment
+- ✅ PR shows ✅ or ❌ status
+- ❌ Build job DOES NOT run (not merged yet)
+
+### Scenario 3: Merge to Main
+
+```bash
+git checkout main
+git merge feature/new-feature
+git push origin main
+```
+
+**What happens:**
+- ✅ Tests run
+- ✅ Integration tests run
+- ✅ Build job runs (creates JAR)
+- ✅ JAR stored as artifact
+
+## Downloading Build Artifacts
+
+1. Go to **Actions** → Select a completed run
+2. Scroll down to **Artifacts** section
+3. Download available artifacts:
+   - `test-reports` - Test HTML reports
+   - `integration-test-reports` - Integration test reports
+   - `library-management-jar` - Built JAR (main/develop only)
+
+## Troubleshooting
+
+### ❌ Build Failed: Tests Failed
+
+**Check what failed:**
+1. Click on the failed workflow
+2. Click on the failed job
+3. Expand the "Run tests" step
+4. See which test failed
+
+**Fix locally:**
+```bash
+mvn clean test
+```
+
+### ❌ Build Failed: Workflow Syntax Error
+
+**Validate syntax:**
+```bash
+# Check YAML is valid
+cat .github/workflows/ci.yml
+```
+
+**Common issues:**
+- Incorrect indentation (use 2 spaces)
+- Missing quotes around values
+- Typos in action names
+
+### ⚠️ Build is Slow
+
+**First build:** 3-4 minutes is normal (downloading deps)
+**Second build:** Should be ~1-2 minutes (cache working)
+
+**If still slow:**
+- Check cache is working (look for "Cache restored" in logs)
+- Maven might be re-downloading dependencies
+
+## Next Steps
+
+### Optional Enhancements
+
+1. **Add code coverage** (see `ci-coverage.yml`):
+   ```bash
+   mv .github/workflows/ci-coverage.yml .github/workflows/ci.yml
+   ```
+
+2. **Set up Codecov** for coverage tracking:
+   - Sign up at codecov.io
+   - Add `CODECOV_TOKEN` to GitHub secrets
+   - Uncomment Codecov step in `ci-coverage.yml`
+
+3. **Add notifications:**
+   - Slack integration
+   - Discord webhooks
+   - Email on failure only
+
+4. **Deploy on success:**
+   - Heroku deployment
+   - Docker image build
+   - AWS/GCP deployment
+
+## Cheat Sheet
+
+### View Logs
+```
+Repository → Actions → Select run → Click job → View logs
+```
+
+### Re-run Failed Build
+```
+Failed run → Re-run all jobs button (top right)
+```
+
+### Cancel Running Build
+```
+Running build → Cancel workflow button (top right)
+```
+
+### Download Artifacts
+```
+Completed run → Scroll to Artifacts → Click to download
+```
+
+### View Test Results
+```
+Completed run → See test summary at top
+Pull Request → See checks section
+```
+
+## Free Tier Limits
+
+**Private repos:** 2,000 minutes/month
+- Your usage: ~2 min/build
+- **You can run ~1,000 builds/month** ✅
+
+**Public repos:** **UNLIMITED** ✅
+
+## Why GitHub Actions > CircleCI
+
+For your project:
+
+| Aspect | GitHub Actions | CircleCI |
+|--------|----------------|----------|
+| Setup | ✅ Zero config | ❌ Signup + OAuth |
+| Cost | ✅ 2,000 min free | 6,000 min free |
+| Integration | ✅ Native | ❌ Third-party |
+| PR Comments | ✅ Built-in | ❌ Requires setup |
+| Artifacts | ✅ Free | ⚠️ Limited |
+| UI | ✅ In GitHub | ❌ Separate site |
+
+**GitHub Actions is the clear winner!** ✅
+
+## Success Checklist
+
+After your first build:
+
+- [ ] Workflow runs successfully
+- [ ] All 46 tests pass
+- [ ] Test results visible in Actions tab
+- [ ] Cache works on second build (faster)
+- [ ] Status badge shows in README (if added)
+- [ ] Artifacts available for download
+
+## What's Running?
+
+Your current setup tests:
+
+```
+✅ 16 UserRepository tests
+✅ 15 BookRepository tests
+✅ 15 BorrowingRepository tests
+─────────────────────────────
+✅ 46 total tests
+```
+
+**All running automatically on every commit!** 🎉
+
+## Get Help
+
+- **Not working?** Check workflow logs in Actions tab
+- **Syntax error?** Validate YAML indentation
+- **Tests failing?** Run `mvn test` locally first
+- **Need more?** Check [README.md](.github/workflows/README.md)
+
+---
+
+**You're all set! Push your code and watch the magic happen.** ✨