Test-PasswordStrength.ps1

function Test-PasswordStrength {
    <#
        .SYNOPSIS
            Test password strength.
        .DESCRIPTION
            This functions lets input a password to test it strength.
        .EXAMPLE
            Test-PasswordStrength 'MyCoolPassword'
        .NOTES
            Based on code example from https://social.msdn.microsoft.com/Forums/vstudio/en-US/5e3f27d2-49af-410a-85a2-3c47e3f77fb1/how-to-check-for-password-strength?forum=csharpgeneral
            Author: Øyvind Kallstad
            Date: 24.09.2015
            Version: 1.0
        .OUTPUTS
            System.String
        .LINK
            https://communary.wordpress.com/
    #>
    [CmdletBinding()]
    param (
        # The password to test
        [Parameter(Position = 0, Mandatory = $true, ValueFromPipeline = $true)]
        [ValidateNotNullOrEmpty()]
        [string] $Password
    )

    $score = 0

    if ($Password.Length -lt 5) {
        Write-Verbose 'Password length is less than 5 characters.'
        Write-Output 'Very Weak'
        break
    }

    if ($Password.Length -ge 8) {
        Write-Verbose 'Password length is equal to or greater than 8 characters. Added 1 to password score.'
        $score++
    }

    if ($Password.Length -ge 12) {
        Write-Verbose 'Password length is equal to or greater than 12 characters. Added 1 to password score.'
        $score++
    }

    if ([regex]::IsMatch($Password, '\d+')) {
        Write-Verbose 'Password contains numbers. Added 1 to password score.'
        $score++
    }

    if ([regex]::IsMatch($Password, '[a-z]+')) {
        Write-Verbose 'Password lowercase letters. Added 1 to password score.'
        $score++
    }

    if ([regex]::IsMatch($Password, '[A-Z]+')) {
        Write-Verbose 'Password uppercase letters. Added 1 to password score.'
        $score++
    }

    if ([regex]::IsMatch($Password, '[!@#$%^&*?_~-£(){},]+')) {
        Write-Verbose 'Password symbols. Added 1 to password score.'
        $score++
    }
    
    switch ($score) {
        1 { $passwordScore = 'Very Weak' }
        2 { $passwordScore = 'Weak' }
        3 { $passwordScore = 'Medium' }
        4 { $passwordScore = 'Strong' }
        5 { $passwordScore = 'Strong' }
        6 { $passwordScore = 'Very Strong' }
    }

    Write-Output $passwordScore
}