Importing tested functions

Migrating from Pester v4? Jump to Migrating from Pester v4.

Importing the tested functions

Pester tests are placed in .Tests.ps1 file, for example Get-Emoji.Tests.ps1. The code is placed in Get-Emoji.ps1.

To make the tested code available to the test we need to import the code file. This is done by dot-sourcing the file into the current scope like this:

Get-Emoji.Tests.ps1

# at the top of the file
BeforeAll {
    . $PSScriptRoot/Get-Emoji.ps1
}

This code will locate the Get-Emoji.ps1 file, which is placed in the same directory as Get-Emoji.Tests.ps1 and import it into the test by dot-sourcing it.

Alternatively $PSCommandPath can be used to get the name of the code file by convention:

Get-Emoji.Tests.ps1

BeforeAll {
    # Get-Emoji.Tests.ps1 - .Tests.ps1 + .ps1 = Get-Emoji.ps1
    . $PSCommandPath.Replace('.Tests.ps1','.ps1')
}

This avoids spelling out the name of the referenced file every time.

warning

The code above is using string.Replace() method which is case sensitive. Make sure you say Tests and that the test file is named .Tests.ps1.

warning

Pester v4 users might be inclined not to use the BeforeAll block or to use $MyInvocation.MyCommand.Path in BeforeAll. Neither will work. See Migrating from Pester v4.

Migrating from Pester v4

Put setup in BeforeAll

In Pester v5 and later the setup code should be put into a BeforeAll block, and $MyInvocation.MyCommand.Path should NOT be used:

# BEFORE (Pester v4):

$here = Split-Path -Parent $MyInvocation.MyCommand.Path
$sut = (Split-Path -Leaf $MyInvocation.MyCommand.Path).Replace(".Tests.", ".")
. "$here\$sut"

Describe "Get-Cactus" {
    It "Returns 🌵" {
        Get-Cactus | Should -Be '🌵'
    }
}

# AFTER (Pester v5+):

BeforeAll {
    # DON'T use $MyInvocation.MyCommand.Path
    . $PSCommandPath.Replace('.Tests.ps1','.ps1')
}

Describe "Get-Cactus" {
    It "Returns 🌵" {
        Get-Cactus | Should -Be '🌵'
    }
}

Using $MyInvocation.MyCommand.Path in other code

$MyInvocation.MyCommand.Path can be used in other parts of your code, just not in BeforeAll. If your module uses it, then it will continue to work even when used with Pester 5. The breaking change in Pester is because the $here\$sut snippet relies on the fact that it runs directly in the script, which is no longer true when placed in BeforeAll. This problem is not specific to BeforeAll, running $MyInvocation.MyCommand.Path in any function will make the Path property undefined:

"in script: -$($MyInvocation.MyCommand.Path)-"

function f () { "in function: -$($MyInvocation.MyCommand.Path)-" }
f

# output:
in script: -C:\temp\script.ps1-
in function: --