Public/SoftwareProduct.ps1

<#
.SYNOPSIS
    Test the installed Software Packages.
.DESCRIPTION
    Test the Existance of a Software Package or the Value of a given Property.
.PARAMETER Target
    Specifies the path to an item.
.PARAMETER Property
    Specifies a property at the specified Path.
.PARAMETER Should
    A Script Block defining a Pester Assertion.
.EXAMPLE
    SoftwareProduct 'Microsoft .NET Framework 4.6.1' { Should Exist }
.EXAMPLE
    SoftwareProduct 'Microsoft SQL Server 2016' DisplayVersion { Should Be 13.0.1100.286 }
.EXAMPLE
    SoftwareProduct 'IIS 10.0 Express' InstallLocation { Should Match 'C:\Program Files (x86)' }
.NOTES
    Assertions: Be, BeExactly, Exist, Match, MatchExactly
#>

function SoftwareProduct {
 
    [CmdletBinding(DefaultParameterSetName="Default")]
    param(        
        [Parameter(Mandatory, Position=1, ParameterSetName="Default")]
        [Parameter(Mandatory, Position=1, ParameterSetName="Property")]
        [Alias("Path")]
        [string]$Target,
        
        [Parameter(Position=2, ParameterSetName="Property")]
        [ValidateSet("DisplayVersion", "InstallLocation", "EstimatedSize")]
        [string]$Property,
        
        [Parameter(Mandatory, Position=2, ParameterSetName="Default")]
        [Parameter(Mandatory, Position=3, ParameterSetName="Property")]
        [scriptblock]$Should
    )
    
    $expression = {@('HKLM:\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*','HKLM:\\Software\Microsoft\Windows\CurrentVersion\Uninstall\*') | Where-Object { Test-Path `$_ } | Get-ItemProperty | Where-Object DisplayName -Match '$Target'}
    
    $params = Get-PoshspecParam -TestName SoftwareProduct -TestExpression $expression @PSBoundParameters
    
    Invoke-PoshspecExpression @params
}