Pester testing framework basics in PowerShell

Introduction

Pester helps you check if your PowerShell scripts work correctly by running tests automatically.

You want to make sure a script returns the right result before using it.

You need to check if a function handles errors as expected.

You want to test parts of your script after making changes to avoid mistakes.

You want to share your script with others and prove it works.

You want to automate testing so you don't have to check manually every time.

Syntax

PowerShell

Describe "Test group name" {
    Context "Specific scenario" {
        It "Test case description" {
            # Test code and assertions here
        }
    }
}

Use Describe to group related tests.

Use It blocks to define individual test cases.

Examples

This test checks if adding 1 and 1 equals 2.

PowerShell

Describe "Math tests" {
    It "Adds numbers correctly" {
        (1 + 1) | Should -Be 2
    }
}

This test checks if an empty string has length zero.

PowerShell

Describe "String tests" {
    Context "When string is empty" {
        It "Has length zero" {
            ''.Length | Should -Be 0
        }
    }
}

Sample Program

This script tests if addition and subtraction work as expected.

PowerShell

Describe "Simple math tests" {
    It "Checks addition" {
        (2 + 3) | Should -Be 5
    }
    It "Checks subtraction" {
        (5 - 2) | Should -Be 3
    }
}

Important Notes

Run Pester tests by saving the script and running it in PowerShell.

Use Should to make assertions about expected results.

Pester is included in Windows PowerShell 5.1 and later, or can be installed via PowerShell Gallery.

Summary

Pester helps automate testing of PowerShell scripts.

Tests are grouped with Describe and written inside It blocks.

Use Should to check if results match expectations.