Test Windows Credential

function Test-Credential
{
    <#
        .SYNOPSIS
            Takes a PSCredential object and validates it against the
            domain (or local machine, or ADAM instance).

        .PARAMETER Credential
            A PSCredential object with the username/password you wish to test.
            Typically this is generated using the Get-Credential cmdlet.
            Accepts pipeline input.

        .PARAMETER Context
            An optional parameter specifying what type of Credential this is.
            Possible values are 'Domain','Machine',and 'ApplicationDirectory.'
            The default is 'Domain.'

        .OUTPUTS
            A boolean, indicating whether the Credentials were successfully validated.
    #>
    param(
        [Parameter(Mandatory, ValueFromPipeline)]
        [ValidateNotNullOrEmpty()]
        [pscredential]
        $Credential,

        [Parameter()]
        [ValidateSet('Domain', 'Machine', 'ApplicationDirectory')]
        [string]
        $Context = 'Domain'
    )

    begin
    {
        Add-Type -AssemblyName System.DirectoryServices.AccountManagement
        $DS = New-Object -TypeName System.DirectoryServices.AccountManagement.PrincipalContext -ArgmentList [System.DirectoryServices.AccountManagement.ContextType]::$Context
    }

    process
    {
        $DS.ValidateCredentials($Credential.UserName, $Credential.GetNetworkCredential().Password)
    }
}