Because I'm too lazy to keep downloading EICAR files.

New-EicarFile.ps1

function New-EicarFile
{
    <#
    .SYNOPSIS
      Creates an EICAR file.
    .DESCRIPTION
      Will generate a file with the EICAR antimalware test string at the given path.
    .PARAMETER Path
      The full path of the file to create.
    .PARAMETER Force
      If the file exists, Force will attempt to overwrite it.
    .INPUTS None
    .OUTPUTS File
    .LINK http://www.eicar.org/86-0-Intended-use.html
    #>
    [CmdletBinding()]
    param(
        [Parameter( Mandatory,
                    Position = 0)]
        [string] $Path,
        [switch] $Force
    )
    
    begin {
        Write-Verbose 'Initializing integer array.'
        $IntArray = @(  88,53,79,33,80,37,64,65,80,91,52,92,80,90,88,53,52,
                        40,80,94,41,55,67,67,41,55,125,36,69,73,67,65,82,45,
                        83,84,65,78,68,65,82,68,45,65,78,84,73,86,73,82,85,
                        83,45,84,69,83,84,45,70,73,76,69,33,36,72,43,72,42
                     )
        $StringBuilder = New-Object System.Text.StringBuilder
    }
    
    process {
        foreach ($int in $IntArray) {
            $char = [char] $int
            
            Write-Verbose ('Adding character {0} (int: {1}) to string.' -f $char,$int)
            $null = $StringBuilder.Append($char)
        }
        
        if (Test-Path $Path -ErrorAction SilentlyContinue) {
            if ($Force) {
                Write-Verbose ('Writing string to file: {0}' -f $Path)
                $StringBuilder.ToString() | Out-File -FilePath $Path -Force
            }
            else {
                Write-Error ('Unable to write file {0} because it already exists. Try another file name, or using the -Force parameter.' -f $Path)
            }
        }
        else {
            Write-Verbose ('Writing string to file: {0}' -f $Path)
            $StringBuilder.ToString() | Out-File -FilePath $Path -Force
        }
    }
}