Jenkins Pipeline: Getting Started Tutorial For Beginners [With Examples]

Why Use Jenkins Pipeline?

As explained above in this Jenkins pipeline tutorial, Jenkins significantly delivers high-quality applications or products. We know that Jenkins has proved to be a specialist in continuous integration, continuous testing, and continuous delivery. It uses a feature called Jenkins pipeline for continuous delivery, which is the ability to release apps regularly at an interval. This process ensures that the software is always ready for production.

To dive deeper into this Jenkins pipeline tutorial, we need to understand the advantages of the Jenkins pipeline.

Advantages of Jenkins Pipeline

The highlight of Jenkins pipeline is that it offers the feature to define the complete deployment flow-through configuration and code. It states that all the standard Jenkins jobs can be written manually as an entire script and managed with a version control system.

It’s essentially following the discipline of ‘pipeline as code.’ Hence, instead of creating multiple jobs for each process, we can code the entire workflow and place it in a Jenkins file. Below are some reasons one might consider before using the Jenkins pipeline for Jenkins test automation with Selenium.

• By using Groovy DSL (Domain Specific Language), it models easy to complex pipelines as code.
• The code is stored as a text file called ‘Jenkinsfile’ that can be scanned into Source Code Management.
• It supports complex pipelines by adding conditional loops, forks, or joining operations and allowing parallel execution tasks.
• It improves user experience by integrating user feedback into the pipeline.
• It’s resilient in terms of unplanned restart.
• It can resume from the checkpoints saved.
• It can incorporate multiple additional plugins and add-ins.

Next up, we will learn about Jenkinsfile in this Jenkins pipeline tutorial.

What is Jenkinsfile?

To proceed with our Jenkins pipeline tutorial, we need to understand the role of Jenkinsfile. It is a text file that stores the whole process as code in our local machine. It can be reviewed in a Source Code Management (SCM) platform like Git. It is instrumental as it helps the developers to view, edit, and test the code whenever required.

The Jenkinsfile is written using the Groovy Domain-Specific Language and can be generated using a text editor or the Jenkins instance configuration tab.

There are two different types in which the Jenkins pipeline can be constructed.

• Declarative pipeline
• Scripted pipeline

Declarative Pipeline

The Declarative pipeline is a recent inclusion in the Jenkins pipeline. It introduces a more streamlined and opinion-driven syntax built upon the existing pipeline sub-systems.

Every valid Declarative pipeline needs to be enclosed within a pipeline block, as illustrated below:

pipeline{
    /* insert Declarative Pipeline here */
}

The fundamental principles and language constructs applicable within the Declarative pipeline adhere to Groovy’s syntax guidelines with particular deviations:

• The primary structure of the pipeline necessitates a block format, specifically enclosed within pipeline .
• Elimination of semicolons as statement separators; each statement requires its line.
• Blocks should comprise Sections, Directives, Steps, or Assignment statements.
• Treating a property reference statement as a no-argument method invocation, such that, for instance, ‘input’ is interpreted as ‘input()’.

Jenkinsfile (Declarative Pipeline)
pipeline {
    agent { docker { image 'maven:3.3.3' } }
    stages {
        stage('build') {
            steps {
                sh 'mvn --version'
            }
        }
    }
}

Generating Jenkins Pipeline Code Using Declarative Directive Generator

The Directive Generator simplifies the process of selecting and configuring Declarative directives, facilitating the creation of respective directive configurations for utilization within the Declarative pipeline.

This tool empowers users to efficiently generate the pipeline code about various Declarative pipeline directives, including agent, options, when, and more. Through an intuitive dropdown menu and a user-friendly form, individuals can precisely define their preferences and values.

Once the form is completed, clicking ‘Generate Declarative Directive’ will showcase the pipeline code in the designated area below. This generated code can be effortlessly copied into the appropriate sections of your Jenkinsfile, either within the pipeline block for overarching directives or within a stage block for directives specific to stages. For further guidance on directives, please consult the online syntax documentation.

Scripted Pipeline

The Scripted pipeline, akin to the Declarative pipeline, is constructed upon the foundational pipeline sub-systems. In contrast to the Declarative approach, the Scripted pipeline functions as a versatile domain-specific language (DSL) developed using Groovy. This enables users to leverage the extensive functionalities offered by the Groovy language, granting significant expressive capabilities and adaptability in constructing continuous delivery pipelines.

Within the Scripted pipeline, execution occurs sequentially, following a top-down approach within a Jenkinsfile, akin to the execution model in conventional Groovy or other scripting languages. Consequently, implementing flow control relies on Groovy expressions, such as conditional statements like if/else constructs.

Jenkinsfile (Scripted Pipeline)
/* Requires the Docker Pipeline plugin */
node('docker') {
    checkout scm
    stage('Build') {
        docker.image('maven:3.3.3').inside {
            sh 'mvn --version'
        }
    }
}

Generating Jenkins Pipeline Code Using Snippet Generator

The Snippet Generator facilitates familiarity with the pipeline script code for defining diverse procedural steps. Select a step of interest from the provided list, configure it as desired, and generate the pipeline script. You’ll obtain a corresponding statement tailored to call that step with your specified configuration. You can copy and paste the entire statement into your script or selectively extract the pertinent options. Note that most parameters are optional and can be excluded from your script, retaining their default values when omitted.

How to Install and Run Jenkins on Windows?

It’s time to get to the best part of this Jenkins pipeline tutorial and start the whole setup process. First of all, we need to install Jenkins. Jenkins can be installed on either Windows, Unix, or macOS systems. In this Jenkins pipeline tutorial, we will concentrate on Windows installation.

Pre-requisites

Before downloading Jenkins on your Windows system, Jenkins needs the following prerequisites:

Hardware Specifications:

• 512 MB of RAM to run Jenkins on your device or laptop.
• 1 GB of storage on your hard drive.

Software Specifications:

• Latest Java Development Kit (JDK) or Java Runtime Environment (JRE) versions based on your system configuration, 32-bit or 64-bit.

You can learn more about setting Jenkins on your system through this blog on setting Jenkins pipeline Environment Variables.

Steps For Installation

Step 1: Once all the prerequisites are met, download Jenkins from this web address https://jenkins.io/download/

Step 2: Once you open the Jenkins download page, you will be prompted to select the platform you intend to download Jenkins. Click on Windows (or other options based on your system). For this Jenkins pipeline tutorial, we will be choosing Windows.

Unzip the downloaded kit. Double-click the unzipped jenkins.msi file. You may also use the .war file to install Jenkins as a Java Package. This is recommended if you are focused on Jenkins test automation with Selenium in non-headless mode.

Step 3: Select Next button to continue the installation of Jenkins on your windows computer or laptop.

Step 4: Select the directory where you’d like Jenkins version to be installed (the default setting is C:\Program Files (x86)\Jenkins), then press the Next tab.

Step 5: Click on Install.

Step 6: Upon finishing the Jenkins setup process, you can continue further and start the setup. The next steps should instruct you on how to unblock the Jenkins submission. Upon completion of the Jenkins installation phase, a window tab will show up requesting for the Administrator’s initial password.

Step 7: You have to proceed to the below path in your web browser to access Jenkins. localhost:8080

Once you can navigate the URL above, it will indicate that Jenkins has been properly installed on the system.

Step 8: The initial Administrator password can be located in the Jenkins setup path. A file named Initial Admin Password can be located at installation-directory >\Jenkins\secrets\ initialAdminPassword

Step 9: Once you have entered the password on the Jenkins login page, you will now be prompted to choose the requisite plugins for your personalized project. You can select the Install suggested plugin for proceeding with the default list of plugins, or you can choose the plugins you want by clicking on Select plugins to install.

You will then see a Getting Started page that will install all the necessary plugins required to get you started with Jenkins CI/CD.

Step 10: Once all the recommended plugins have been downloaded, the Create First Admin User tab will appear. Fill all boxes with the account info you like and press the Save and Continue option.

Step 11: Once this information is duly filled, a webpage may ask you for URL data. This URL is utilized to set the default configuration path for Jenkins. Keep it as it is to prevent any confusion later on. Nevertheless, if another program is still utilizing an 8080 port, you can either stop that program from using the port and make Jenkins’ space and then save the settings.

Or you can change the port number, which we recommend in this Jenkins pipeline tutorial. To change the port, go to < Jenkins-installation-folder >\Jenkins\jenkins.xml

Search for the httpPort and change it from 8080 to any port number of your choice. Jenkins is set to listen to port 8080 by default.

You might be prompted to have administrator rights for implementing this port change. Follow this-

<service>
  <id>Jenkins</id>
  <name>Jenkins</name>
  <description>This service runs Jenkins automation server.</description>
  <env name="JENKINS_HOME" value="%BASE%"/>
  <!--
    if you'd like to run Jenkins with a specific version of Java version, specify a full path to java.exe.
    The following value assumes that you have java in your PATH.
  -->
  <executable>%BASE%jreinjava</executable>
  <arguments>-Xrs -Xmx256m -Dhudson.lifecycle=hudson.lifecycle.WindowsServiceLifecycle -jar "%BASE%jenkins.war" --httpPort=9090 --webroot="%BASE%war"</arguments>

Once you do this, you’re through with Jenkins deployment. After this step, the Jenkins account will be set up and is ready to use.

Step 12: Jenkins is enabled, and we’re almost finished. Before we switch to build as per this Jenkins pipeline tutorial, we will need to customize Jenkins to recognize other resources like Java, Maven, etc.

Click on ‘Manage Jenkins.’ After this, select ‘Global Tool Configuration’ and ‘JDK Installation.’ Include the JDK version’s name in the JDK Name line and access the Java route in the ‘JAVA_HOME’ portion.

Uncheck the ‘Install Automatically’ radio option because there might be a risk that Selenium may not help if the latest Java version is modified. Save the changes and continue.

Jenkins Pipeline Concepts

We hope that Jenkins is up and running in your Windows system, following the steps mentioned above in this Jenkins pipeline tutorial. Before moving ahead with Jenkins test automation with Selenium, it is time to get accustomed to some of the crucial concepts of this Jenkins pipeline tutorial. Here they are

Pipeline

It is a user-defined framework that includes all the processes like create, check, deploy, etc. In a Jenkinsfile, it’s a list of all the levels. All of the stages and steps within this block are described. This is the fundamental block to the syntax of a declarative pipeline.

pipeline  {
 }

Node

A node is a system running a complete workflow. It’s an integral part of the syntax of the scripted pipeline.

node  { 
}

Some standard sections are available to declarative and scripted pipelines. These are:

Agent

An agent is described as a directive that can run multiple builds using just one Jenkins instance. This feature helps spread the workload to various agents and execute multiple projects within Jenkins’s single instance. It instructs Jenkins to assign the builds to an executor.

A single agent may be defined for a whole Jenkins pipeline or different agents may be assigned to execute each stage within a pipeline. Some of the most commonly used Agent parameters are:

• Any: Runs the stage pipeline on any available agent.
• None: This parameter is added to the root of the pipeline. It means there is no global agent for the entire pipeline, and each stage must define its agent.
• Label: Performs on the labeled agent in the pipeline/stage.
• Docker: This parameter uses a docker container as a pipeline execution environment or as a specific level. For example, the docker can pull an image of Ubuntu. This image can now run multiple commands as an execution environment.

pipeline { 
    agent { 
        docker { 
            image  'ubuntu'
                }
            }
        }

Stages

This section includes all of the work that needs to be completed. The work is defined in the form of stages. Within this Directive, there may be more than one level. Each stage executes a particular task.

pipeline { 
agent any 
    stages { 
        stage ('Build') { 
 
        }
        stage ('Test') { 
        
        }
        stage ('QA') { 
        
        }
        stage ('Deploy') { 
        
        }
        stage ('Monitor') { 
 
        }
 
    }           
 }

Steps

Within a stage block, the pipeline can be described as a series of steps. Such steps are performed in sequence for the execution of a level. Within a Steps guideline, there must be at least one step.

pipeline { 
    agent any 
        stages { 
            stage ('Build') { 
                steps { 
                    echo 
                    'Running build phase. ' 
                }
            }
        }
    }

Integrating Jenkins Pipeline with Cloud Selenium Grid

The point of this Jenkins pipeline tutorial was not just to get acquainted with Jenkins or the pipeline itself. Yes, we wanted to help you set up a Jenkins pipeline but then you must be wondering what’s the purpose of this entire setup. As pointed out earlier in this Jenkins pipeline tutorial, Jenkins pipeline is quite helpful in executing Selenium. To implement this, Jenkins provides various plugins for integration with various tools and utilities while monitoring productivity.

To start with Jenkins test automation with Selenium, TestMu AI Jenkins plugin is one such plugin to help you speed up automated cross browser testing. With the TestMu AI Jenkins plugin, we can easily automate our test scripts by connecting the Jenkins CI instance to the TestMu AI Selenium grid.

TestMu AI Selenium grid offers a range of 3000 + browsers and browser versions to achieve higher browser coverage to conduct cross browser testing.

Integrating Jenkins with TestMu AI will increase your test quality and coverage by

• Configuring the credentials for TestMu AI and the job scheduled with Jenkins.
• Performing a setup and tearing down the binary TestMu AI Tunnel file to conduct automated cross browser testing even on your local web applications.
• Providing all test data, such as video logs, network logs, and screenshots, in each step performed at various stages with your Jenkins job via TestMu AI.

For Jenkins test automation with Selenium, you would require access to the following:

• A TestMu AI account.
• An existing server with the Jenkins CI (version 2.138.2+)
• A root-access Jenkins Client.

Configuring TestMu AI Jenkins Plugin

To move ahead with the most exciting section of this Jenkins pipeline tutorial, we would need to download the TestMu AI Jenkins plugin, as explained below, to run our Selenium tests on TestMu AI using Jenkins. Before installing Jenkins, access to the administrator level is required.

Before installing the TestMu AI Jenkins plugin, ensure no active build jobs in execution or queue.

Step 1: First, we click on Manage Jenkins and then Manage Plugins.Step 2: Then, we navigate and click on the Available tab.Step 3: Search for TestMu AI in the filter search box on the tab.Step 4: You will find a list of plugins on which to proceed and select TestMu AI.Step 5: To install the TestMu AI Jenkins plugin, select the checkbox before TestMu AI.Step 6: After successfully installing the plugin, you can find the TestMu AI Jenkins plugin under your installed plugins.

Sometimes, your newly installed plugins fail to synchronize with the Jenkins plugins you have available. This is quite common. You can do this if you fail to find TestMu AI under your available plugins section. Refresh the Jenkins plugin list by simply clicking the Check Now button, and you will get a list with new plugins from the Jenkins update center.

Once the TestMu AI Jenkins plugin is installed, we must integrate our Selenium WebDriver tests with Jenkins by configuring the TestMu AI credentials in the Jenkins CI server. This step is essential to proceed with Jenkins test automation using Selenium or perform automated cross browser testing.

Configuring TestMu AI Credentials

To proceed with this Jenkins pipeline tutorial configuration, we would need to work with the Jenkins UI. We don’t have to prepare the script from scratch to execute the test. We can reuse our local test script and add some minor configuration changes that will enable us to connect to the cloud platform.

One of the most vital things for us to communicate to the TestMu AI platform is to get our access key token. The access key tokens are private keys that enable us to connect to the cloud platform and execute automated tests. This access key is unique for everyone and should not be shared with other users. You can fetch and regenerate it from the Profile section of your user account, as shown below.

Alternatively, we can fetch the access key, username, and hub details from the Web Automation Dashboard. You’ll need to click the key-shaped icon near the Help button, as shown in the image screenshot below.

This can be set as below in the script-

$ export LT_USERNAME= {your lambdatest username} 
 
$ export LT_ACCESS_KEY= {your lambdatest access_key}

$ set LT_USERNAME= {your lambdatest username}
 
$ set LT_ACCESS_KEY= {your lambdatest access_key}

• Click Credentials on Jenkins Home Page.
• Select System under the Credentials tab to display the System page.
• Select Global Domain credentials (Unrestricted) in the System to open the page for Global credentials.
• Click on Add Credentials to open the credentials page where we add the access details.
• Enter relevant data in all the fields and click Verify Credentials.
• Then click the OK button after verification.
• Jenkins generates the ID on the Credential page, and we save the changes.

After successfully attaching your credentials, Jenkins creates an ID. To get this ID for using TestMu AI credentials, you’d need to go to Jenkins’s homepage and click on the Credentials tab on the left side of the navigation screen.

From the Jenkins home page, click on Credentials from the menu on the left. TestMu AI credentials can be copied from this ID.

Next, we would need to use the TestMu AI Jenkins plugin to enable TestMu AI Tunnel to perform cross browser testing on locally hosted web pages or files.