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Version: v4

Installation and Update


Pester is compatible with every version of Windows that can run at least PowerShell 2. That is Windows 10, 8, 7, Vista, XP, and their respective Server versions 2016, 2012 R2, 2012, 2008 R2, 2008, and 2003.

Installing from PSGallery Windows 10 or Windows Server 2016

Windows 10 and Windows Server 2016 make installing and updating PowerShell modules extremely simple by providing Install-Module and Update-Module cmdlets. Unfortunately there are some complications specific to Pester, that we cannot avoid.

Pester version 3.4.0 ships as part of Windows 10 and Windows server 2016, and that distribution conflicts with the standard module update mechanism. It is not possible to update the built-in Pester to newer version, using the Update-Module cmdlet.

Instead you need to perform a new side-by-side installation of Pester, because Install-Module detects the current installation of Pester is signed with a different signature than the one you are installing.

Here's the command you need to run as administrator in order to get the latest version of Pester:

Install-Module -Name Pester -Force

Installing the module may result in this message:

WARNING: Module 'Pester' version '3.4.0' published by
'CN=Microsoft Windows, O=Microsoft Corporation, L=Redmond, S=Washington, C=US'
will be superceded by version '4.4.3' published by 'CN=Jakub Jareš, O=Jakub Jareš,
L=Praha, C=CZ'. If you do not trust the new publisher, uninstall the module.

This is because the module is signed by a different certificate than the version that Microsoft shipped with Windows.

In Windows 10 v1809 and higher, you first need to cleanup the default Pester module and only then you can proceed with the installation of higher version of Pester module

$module = "C:\Program Files\WindowsPowerShell\Modules\Pester"
takeown /F $module /A /R
icacls $module /reset
icacls $module /grant "*S-1-5-32-544:F" /inheritance:d /T
Remove-Item -Path $module -Recurse -Force -Confirm:$false

Install-Module -Name Pester -Force

For any subsequent update it is enough to run:

Update-Module -Name Pester

Installing from PSGallery on other versions of Windows

The way you can install a new module differs based on the version of PowerShell you are using. Determine the version of PowerShell you are using by running:


PowerShell 5 or newer

In version 5 or newer you can use the built-in Install-Module and Update-Module cmdlets coming from PowerShellGet.

From administrator PowerShell command line run:

Install-Module -Name Pester

Or to update:

Update-Module -Name Pester

PowerShell 3 and 4

On PowerShell 3 and 4, there is no default package manager installed, but luckily PowerShellGet is available for installation. See detailed instructions here. When you have the package manager installed, please start a new administrator PowerShell window and use:

Install-Module -Name Pester

Or to update:

Update-Module -Name Pester

PowerShell 2

On PowerShell 2 you can use an alternative to PowerShellGet called PSGet. See installation instructions here. When you have the package manager installed, please start a new administrator PowerShell window and use:

Install-Module -Module Pester

Or to update:

Update-Module -Module Pester

Installing from sources

To install Pester you don't have to use any package manager. You can download the sources directly at our release page and copy them to your Module directory. Your module directory is most likely C:\Program Files\WindowsPowerShell\Modules\Pester or C:\Windows\System32\WindowsPowerShell\v1.0\Modules (on older versions of Windows), please refer to $env:PSModulePath and this article .

This approach can also be used to get unreleased versions of Pester, by clicking the Clone or download button on the main page, or clicking this link.

Alternative package sources

PSGallery is the easiest way to get Pester installed to your computer, but there are alternatives. on a build server you might prefer using Chocolatey, or Pester to your .NET project that already uses nuget, you might prefer using Nuget. not support pre-release versions and it needs to be initialized on first use. For those reasons you might prefer installing from other sources, especial.


Chocolatey (or choco) is the easiest way to get Pester running on AppVeyor. You avoid setting up PowerShellGet and it also supports pre-release versions.

choco install Pester

Or to update:

choco install Pester --prerelease


Nuget is the package manager for .NET projects. Getting Pester from Nuget is useful when you are integrating PowerShell code with your .NET project, and want to have that code tested. To install use Package Manager of Visual Studio, or Package Manager Console in Visual Studio. Once you need this we are pretty sure you know what you are doing. :)