# Jenkins For Automation Testing # βš™οΈ **Jenkins Overview** ## 1️⃣ What is Jenkins? πŸ‘‰ Jenkins is an **open-source automation server** used to implement **Continuous Integration (CI)** and **Continuous Delivery/Deployment (CD)**. It automates: * Building projects * Running tests * Deploying applications So instead of manually running builds/tests/deployments, Jenkins automates everything. --- ## 2️⃣ Why Jenkins came? Before Jenkins (early 2000s), developers: * Built projects manually β†’ time-consuming & error-prone. * Integrated code once in a while ("integration hell"). * Deployment was manual, risky, and slow. πŸ‘‰ Jenkins solved these by **automating CI/CD pipelines** β†’ code is integrated, tested, and deployed automatically. --- ## 3️⃣ When Jenkins came? * Jenkins was created in **2004** by **Kohsuke Kawaguchi** at Sun Microsystems. * Initially called **Hudson**, renamed to **Jenkins** in **2011** (after Oracle dispute). --- ## 4️⃣ What problem does Jenkins solve? * **Automation** β†’ no manual builds/tests/deploys. * **Faster feedback** β†’ catch bugs early with CI. * **Scalability** β†’ master-agent setup for distributed builds. * **Consistency** β†’ same process across all environments. * **Integration** β†’ works with Git, Maven, Selenium, Docker, Kubernetes, etc. πŸ‘‰ In short: Jenkins automates **software delivery pipeline** end-to-end. --- ## 5️⃣ Where can we use Jenkins? * **Automation Testing** β†’ run Selenium/TestNG/JUnit tests. * **DevOps CI/CD** β†’ build β†’ test β†’ deploy pipelines. * **Infrastructure as Code** β†’ integrate with Docker, Kubernetes, Terraform. * **Monitoring** β†’ send reports via Email/Slack. * **Enterprise Projects** β†’ distributed build and deployment pipelines. --- ## 6️⃣ When do we use Jenkins? * When you want **continuous integration** β†’ automatically test code after each commit. * When you want **continuous delivery/deployment** β†’ automatically deploy after successful tests. * When working with **teams** β†’ so every developer’s code gets integrated and tested daily. --- ## 7️⃣ Prerequisite Knowledge for Jenkins Before learning Jenkins, you should know: 1. **Core Java** (for Selenium/TestNG projects). 2. **Maven/Gradle** (build tools Jenkins integrates with). 3. **Git/GitHub** (source code management). 4. **Basic Linux/Windows commands**. 5. **Automation Testing (Selenium/TestNG/JUnit)**. 6. (Optional) **Docker, Kubernetes, Cloud (AWS/Azure/GCP)** if you want to learn DevOps CI/CD. --- βœ… So in summary: * **Maven** automates builds & dependency management. * **Jenkins** automates the entire CI/CD pipeline (build β†’ test β†’ deploy). Perfect πŸ‘ Let’s break down **Jenkins components** in detail with their roles. --- # 🧩 **Jenkins Components & Their Work** --- ## 1️⃣ **Jenkins Server (Master/Controller)** * The **core of Jenkins**. * Provides the **web UI** ([`http://localhost:8080`](http://localhost:8080)). * Stores configuration, jobs, plugins. * Assigns work to agents (slaves). * Monitors builds and shows results. πŸ‘‰ Think of it as the **brain of Jenkins**. --- ## 2️⃣ **Jenkins Nodes (Agents/Slaves)** * Machines that **execute the jobs** assigned by the Master. * Can be physical servers, VMs, or cloud instances. * Each node has labels (e.g., *Windows*, *Linux*, *Docker*) so jobs can run in the right environment. πŸ‘‰ Master tells agents *what to do*, agents actually **do the work**. --- ## 3️⃣ **Jenkins Jobs / Projects** * A **job** is a task Jenkins performs (e.g., build, test, deploy). * Types: * **Freestyle Project** β†’ simple jobs with manual config. * **Maven Project** β†’ integrates with Maven lifecycle. * **Pipeline Project** β†’ scripted with `Jenkinsfile`. * **Multibranch Pipeline** β†’ CI/CD for multiple Git branches. πŸ‘‰ Jobs are the **heart of Jenkins automation**. --- ## 4️⃣ **Jenkins Pipelines** * A way to define the CI/CD workflow as **code (Jenkinsfile)**. * Two types: * **Declarative Pipeline** β†’ simpler, structured. * **Scripted Pipeline** β†’ full flexibility with Groovy scripting. * Consists of **Stages** (`Build`, `Test`, `Deploy`) and **Steps** (commands inside stages). πŸ‘‰ Pipelines = **Automation as Code**. --- ## 5️⃣ **Jenkins Plugins** * Jenkins is lightweight by default. * Plugins extend functionality: * Git plugin β†’ SCM * Maven plugin β†’ build automation * JUnit/TestNG plugin β†’ test reports * Email/Slack plugin β†’ notifications * Allure/Extent β†’ test reporting * Docker/Kubernetes β†’ DevOps integration πŸ‘‰ Over **1800+ plugins** available. --- ## 6️⃣ **Jenkins Workspace** * A **directory on the agent machine** where Jenkins checks out the project code and runs builds. * Example: ```xml /var/lib/jenkins/workspace/MyProject/ ``` * Contains source code, compiled classes, reports, and logs. πŸ‘‰ Each job has its **own workspace**. --- ## 7️⃣ **Jenkins Build Triggers** * Defines *when* a job runs: * **Manual Trigger** β†’ click "Build Now". * **Poll SCM** β†’ check Git repo every X minutes. * **Webhooks** β†’ trigger instantly when code is pushed. * **Scheduled (Cron)** β†’ e.g., nightly builds. * **Upstream/Downstream** β†’ trigger job chains. πŸ‘‰ Triggers = **automation entry point**. --- ## 8️⃣ **Jenkins Build Executors** * Executors are **slots on an agent** that run jobs in parallel. * Example: * 1 agent with 2 executors β†’ can run 2 builds at the same time. πŸ‘‰ Executors = **multi-tasking power of Jenkins**. --- ## 9️⃣ **Jenkins Artifacts** * The **output** of a Jenkins job (e.g., JAR, WAR, ZIP, reports). * Stored in `workspace/target` and can be **archived** in Jenkins. * Used for deployments. πŸ‘‰ Artifacts = **deliverables**. --- ## πŸ”Ÿ **Jenkins Console Output (Logs)** * Shows **step-by-step execution logs** of a job. * Useful for debugging build/test failures. πŸ‘‰ Think of it as Jenkins’ **black box recorder**. --- ## 1️⃣1️⃣ **Jenkins Security & Credentials** * Manages **user authentication & authorization**. * Stores **secrets** (API keys, passwords, SSH keys) securely. * Credentials are injected into jobs when required. πŸ‘‰ Ensures builds are **safe & secure**. --- ## 1️⃣2️⃣ **Jenkins Shared Libraries** * Custom reusable Groovy code for pipelines. * Helps maintain **DRY principle** (Don’t Repeat Yourself). πŸ‘‰ Useful for **enterprise-level pipelines**. --- # 🎯 Summary (One-liner for each component) * **Server (Master/Controller)** β†’ Brains of Jenkins. * **Nodes (Agents/Slaves)** β†’ Workers that execute jobs. * **Jobs/Projects** β†’ The actual tasks. * **Pipelines** β†’ Workflow as code. * **Plugins** β†’ Extend Jenkins features. * **Workspace** β†’ Directory for build execution. * **Triggers** β†’ When jobs run. * **Executors** β†’ Parallel job slots. * **Artifacts** β†’ Build outputs. * **Console Output** β†’ Logs. * **Security & Credentials** β†’ Safe access. * **Shared Libraries** β†’ Reusable pipeline code.