Running unit tests in pipeline in Jenkins - Step-by-Step Execution

Process Flow - Running unit tests in pipeline

Start Pipeline

↓

Checkout Code

↓

Run Unit Tests

↓

Tests Pass?

No→Fail Pipeline

Yes↓

Continue Pipeline / Deploy

The pipeline starts by getting the code, then runs unit tests. If tests pass, it continues; if not, it stops.

Execution Sample

Jenkins

pipeline {
  agent any
  stages {
    stage('Test') {
      steps {
        sh 'pytest'
      }
    }
  }
}

This Jenkins pipeline runs unit tests using pytest in the 'Test' stage.

Process Table

Step	Action	Command Run	Result	Pipeline State
1	Start Pipeline	N/A	Pipeline started	Running
2	Checkout Code	git checkout main	Code checked out	Running
3	Run Unit Tests	pytest	Tests running	Running
4	Tests Pass?	pytest exit code 0	All tests passed	Running
5	Continue Pipeline	N/A	Proceed to next stage or deploy	Success

💡 Pipeline stops if tests fail (non-zero exit code), here tests passed so pipeline continues.

Status Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
pipeline_state	Not started	Running	Running	Running	Success
tests_status	Not run	Not run	Running	Passed	Passed

Key Moments - 2 Insights

Why does the pipeline stop if tests fail?

Because the test command returns a non-zero exit code, Jenkins marks the stage as failed and stops the pipeline (see execution_table step 4).

What does 'pytest exit code 0' mean?

It means all tests passed successfully, so the pipeline can continue (see execution_table step 4).

Visual Quiz - 3 Questions

Look at the execution table, what is the pipeline state after running unit tests?

A Running

B Failed

C Success

D Not started

💡 Hint

Check the 'Pipeline State' column at step 3 in the execution_table.

At which step does the pipeline decide to stop if tests fail?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at the 'Tests Pass?' decision in execution_table step 4.

If pytest returns a non-zero exit code, how would the pipeline state change in the variable tracker?

A pipeline_state would be 'Success'

B pipeline_state would be 'Failed'

C tests_status would be 'Passed'

D tests_status would be 'Not run'

💡 Hint

Refer to variable_tracker 'pipeline_state' changes when tests fail.

Concept Snapshot

Jenkins pipeline runs unit tests in a stage.
If tests pass (exit code 0), pipeline continues.
If tests fail (non-zero exit code), pipeline stops.
Use 'sh' step to run test commands like 'pytest'.
Check exit codes to control pipeline flow.

Full Transcript

This Jenkins pipeline example shows how unit tests run inside a pipeline stage. The pipeline starts, checks out code, then runs tests using the 'pytest' command. If tests pass with exit code 0, the pipeline continues to the next stage or deployment. If tests fail, the pipeline stops immediately. The execution table traces each step, showing pipeline state changes and test results. The variable tracker records the pipeline state and test status after each step. Key moments clarify why the pipeline stops on test failure and what exit codes mean. The quiz tests understanding of pipeline state and decision points based on the execution visuals.