Test-Credential.ps1

<#
.SYNOPSIS
    Test a Domain Targeted PSCredential Object for valid Username and Password.
.DESCRIPTION
    Simulates an Authentication Request in a Domain envrionment using a PSCredential Object.
    Returns $true if both Username and Password pair are valid.
.EXAMPLE
    Test-Credential
.NOTES
    Expansion from Stack Overflow Artical: http://stackoverflow.com/questions/10802850/validating-powershell-pscredential
.LINK
    http://dotps1.github.io
#>
function Test-Credential
{
    [CmdletBinding()]
    [OutputType([Bool])]
    Param
    (
        # Credential, Type PSCredential, The PSCredential Object to test.
        [Parameter(Position = 0,
                   ValueFromPipeLine = $true)]
        [PSCredential]
        $Credential,

        # Domain, Type String, The domain name to test PSCredetianl Object against.
        [Parameter(Position = 1)]
        [String]
        $Domain = $env:USERDOMAIN
    )

    Begin
    {
        if (-not($PSBoundParameters.ContainsValue($Credential)))
        {
            $Credential = Get-Credential
        }
        
        [void][System.Reflection.Assembly]::LoadWithPartialName("System.DirectoryServices.AccountManagement")
        $principalContext = New-Object System.DirectoryServices.AccountManagement.PrincipalContext([System.DirectoryServices.AccountManagement.ContextType]::Domain, $Domain)
    }

    Process
    {
        $networkCredetial = $Credential.GetNetworkCredential()
        return $principalContext.ValidateCredentials($networkCredetial.UserName, $networkCredetial.Password)
    }

    End
    {
        $principalContext.Dispose()
    }
}