how does jenkins pipeline work code example

Example 1: what is jenkins pipeline

Pipeline is a set of processes that take 
the code from version control and compile,
build, test and deploy to
production in automated fashion.
• The pipeline breaks down the software
delivery process into stages.
Each stage is made of different tasks
which can be carried out in parallel. 
When all tasks in a stage passes, next stage is triggered

Example 2: how do you use jenkins

How did you create a Job in jenkins? 
In my company devops team maintains 
the jenkins and as a tester my jenkins
account user do not have enough privilege 
to create new jobs. I provide them server
specifications which means minimum capacity
of the jenkins server (maven, java 8, browser
types(chrome, firefox or what you need), OS(Mac-Windows), etc).
I can only run the jobs and see the results. 
To create my smoke tests on jenkins I created 
a ticket in jira for the devops team. 
But also know how to create and configure 
jenkins jobs myself. 
I have done it in my previous projects. 

How you configure a job(build) in Jenkins?
As a test engineer I only configured 
my smoke tests on jenkins. 
how we configure our smoke test also depend
s on what tools we have in our framework.
I have a cucumber + junit + maven framework. 
So this is how that job is configured:

1. Source Code Management
Here we specify where to get the code from.
we put the link of our GitHub repo 
and also enter the credentials

2. Build Triggers
We specify how often we run those tests.
we choose Build periodically because we
want to run in certain schedule. 
in my project, we run smoke tests every morning.
so in the build trigger we entered daily option:
H 6 * * * --> every day around 6 am.
Jenkins used a cron expression, and the different fields are:

  H * * * *   ==> Build every hour at any minute (6.12 am, 8.38pm)
  0 * * * *   ==> Build every hour at exactly on the hour (6.00 am, 8.00pm)
  0 8 * * *   ==> Build every day exactly 8.00 am
  H/5 * * * * ==> Build every 5 minutes
  H 6 * * 1-5 ==> Build around 6 am from first day of the week (Monday) to 5th day (Friday)
  H 1 * 6,20 * * ==> Build on 6th and 20th day of the month around 1 am for regression

3. Build
Here we enter the details of the actual Run.
since my project is based on maven, 
I choose option: Invoke top-level maven targets
then I choose which maven to run from the
version dropdown. in the next field, 
I enter the maven goal: verify. in this field
we do not need to enter the word mvn.
I can also mention here which tag or which
runner class I want to run. So the command will be:
	verify -Dcucumber.options="--tags @smoke"       ==> for smoke test
	verify -Dcucumber.options="--tags @regression"  ==> for regression test

4. Add Post-build Actions
In the post build actions, we configure
what we want to do after build. after
each test we generate report and email
a. report
We generate report using Cucumber reports plugin.
I select Cucumber reports plugin from the
Post-build Actions to generate reports. 
b. Email
Using the email plugin we can send email
after every build. I select Editable Email
Notification option from the Post-build
Actions to send emails.