Temperature Converter — Jenkins CI/CD Pipeline

A temperature unit converter (Celsius, Fahrenheit, Kelvin) built with Node.js and paired with a complete Jenkins CI/CD pipeline demonstrating automated build, test, Docker image creation, and deployment stages.

The application itself is deliberately simple — the purpose of this project is to demonstrate a production-quality DevOps pipeline configuration that can be adapted to any Node.js project.

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Table of Contents

• Application Overview
• Pipeline Overview
• Tech Stack
• Prerequisites
• Local Setup
• Running the Converter
• Running Tests
• Jenkins Pipeline Configuration
• Docker
• Project Structure
• Conversion Formulas
• Contributing
• License

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Application Overview

The converter exposes both a programmatic API (importable Node.js module) and a simple CLI for quick conversions:

node app.js 100 C F     # 100 Celsius → Fahrenheit → 212
node app.js 32  F C     # 32 Fahrenheit → Celsius → 0
node app.js 0   C K     # 0 Celsius → Kelvin → 273.15

It is fully unit-tested with 100% code coverage and validates all inputs before processing.

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Pipeline Overview

┌──────────┐    ┌──────────┐    ┌──────────┐    ┌──────────┐    ┌──────────┐
│ Checkout │ -> │ Install  │ -> │   Test   │ -> │  Build   │ -> │  Deploy  │
│   Code   │    │   Deps   │    │ Coverage │    │  Docker  │    │   Image  │
└──────────┘    └──────────┘    └──────────┘    └──────────┘    └──────────┘

Every push to main or develop triggers the full pipeline. Pull requests trigger up to the Test stage only (no deployment).

Stage breakdown

Stage	Command	Failure behavior
Checkout	SCM checkout	Abort
Install	npm ci	Abort
Lint	npm run lint	Fail build
Test	npm test -- --coverage	Fail build
Coverage Gate	Enforce >= 80%	Fail build
Build Image	docker build	Fail build
Push Image	Push to registry	Fail build
Deploy	Rolling update	Notify only

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Tech Stack

Component	Technology
Runtime	Node.js 18.x
Testing	Jest 29.x
Linting	ESLint
CI/CD	Jenkins 2.x
Containerization	Docker 24.x
Registry	Docker Hub or private registry

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Prerequisites

For local development:

• Node.js >= 16.0.0
• npm >= 8.0.0

For the full pipeline:

• Jenkins server with the following plugins:
  • Pipeline
  • Docker Pipeline
  • Git
  • JUnit (for test result publishing)
  • Cobertura or Coverage (for coverage reports)
• Docker installed on the Jenkins agent
• Access to a Docker registry (Docker Hub or private)

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Local Setup

git clone https://github.com/Salmanahmed1078/Temperature-Converter-Jenkines-Pipeline.git
cd Temperature-Converter-Jenkines-Pipeline
npm install

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Running the Converter

CLI usage

node app.js <value> <from_unit> <to_unit>

Argument	Valid values
value	Any number (integer or decimal)
from_unit	C (Celsius), F (Fahrenheit), K (Kelvin)
to_unit	C, F, or K (different from from_unit)

Examples:

node app.js 37 C F      # Body temperature: 98.6°F
node app.js 212 F C     # Boiling point: 100°C
node app.js 300 K C     # 300K in Celsius: 26.85°C
node app.js -40 C F     # -40°C = -40°F (they converge here)

Programmatic usage

const { convert } = require('./src/converter');

console.log(convert(100, 'C', 'F'));   // 212
console.log(convert(32,  'F', 'C'));   // 0
console.log(convert(0,   'C', 'K'));   // 273.15
console.log(convert(373.15, 'K', 'F')); // 212

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Running Tests

# Run all tests
npm test

# Run with coverage report
npm run test:coverage

# Watch mode during development
npm run test:watch

Coverage output is written to coverage/ and also published as a Jenkins artifact. The pipeline enforces a minimum 80% coverage threshold — builds below this threshold are marked as failed.

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Jenkins Pipeline Configuration

1. Create a Jenkins Pipeline job

In Jenkins:

1. New Item > Pipeline
2. Under Pipeline, select Pipeline script from SCM
3. SCM: Git, Repository URL: your fork URL
4. Script Path: Jenkinsfile

2. Add credentials

In Jenkins > Credentials, add:

• DOCKER_CREDENTIALS — Docker Hub username and password
• DEPLOY_SSH_KEY — SSH private key for deployment target (if applicable)

3. Environment variables in Jenkinsfile

The Jenkinsfile reads the following environment variables:

environment {
    DOCKER_IMAGE = 'your-dockerhub-username/temperature-converter'
    DOCKER_TAG   = "${BUILD_NUMBER}"
    REGISTRY     = 'https://registry.hub.docker.com'
}

Edit these in the Jenkinsfile before running the pipeline.

4. Trigger the pipeline

Push any commit to main — the webhook (configured in Jenkins > your repo) triggers the pipeline automatically. Or click Build Now to trigger manually.

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Docker

Build the image locally

docker build -t temperature-converter:latest .

Run the container

docker run --rm temperature-converter:latest node app.js 100 C F
# Output: 212

Docker Compose (optional, for extended setups)

docker-compose up

This starts the converter with a simple HTTP wrapper at http://localhost:3000:

curl "http://localhost:3000/convert?value=100&from=C&to=F"
# {"result": 212, "unit": "F"}

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Project Structure

Temperature-Converter-Jenkines-Pipeline/
├── src/
│   ├── converter.js        # Core conversion logic
│   ├── validator.js        # Input validation
│   └── units.js            # Unit constants and metadata
├── tests/
│   ├── converter.test.js   # Unit tests for all conversions
│   ├── validator.test.js   # Input validation tests
│   └── edge-cases.test.js  # Boundary and error conditions
├── app.js                  # CLI entry point
├── server.js               # Optional HTTP wrapper
├── Jenkinsfile             # Pipeline definition
├── Dockerfile
├── docker-compose.yml
├── .eslintrc.js
├── jest.config.js
└── package.json

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Conversion Formulas

From	To	Formula
Celsius	Fahrenheit	(C × 9/5) + 32
Celsius	Kelvin	C + 273.15
Fahrenheit	Celsius	(F − 32) × 5/9
Fahrenheit	Kelvin	(F − 32) × 5/9 + 273.15
Kelvin	Celsius	K − 273.15
Kelvin	Fahrenheit	(K − 273.15) × 9/5 + 32

All results are rounded to 2 decimal places unless the result is a whole number.

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Contributing

1. Fork the repository
2. Create a feature branch: git checkout -b feat/your-feature
3. Ensure npm run lint and npm test both pass
4. Open a pull request with a clear description

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License

MIT © Salman Ahmed