Private/Test/Test-IsWindows.ps1

function Test-IsWindows {
    <#
        .SYNOPSIS
        Tests if the current session is running on Windows.
 
        .DESCRIPTION
        Returns $true if running on a Windows operating system.
        Works across Windows PowerShell 5.1 and PowerShell 6+ (cross-platform).
        In PowerShell 5.1 or earlier, always returns $true (Windows-only versions).
        In PowerShell 6+, checks the $IsWindows automatic variable.
 
        .INPUTS
        None. This function does not accept pipeline input.
 
        .OUTPUTS
        System.Boolean
        Returns $true if running on Windows, $false otherwise.
 
        .EXAMPLE
        Test-IsWindows
        Returns $true if the current session is running on Windows.
 
        .EXAMPLE
        if (Test-IsWindows) {
            Write-Host "Running on Windows"
        }
        Conditionally executes code only on Windows systems.
 
        .LINK
        https://docs.microsoft.com/powershell/module/microsoft.powershell.core/about/about_automatic_variables#iswindows
    #>

    [CmdletBinding()]
    [OutputType([bool])]
    param (
    )

    #requires -Version 5.1

    $result = [bool](($PSVersionTable.PSVersion.Major -le 5) -or $IsWindows)
    Write-Verbose "Windows OS: $result"
    
    $result
}