$servers = Get-Content computers.txt
Write-Output "computer;connect" | Out-File outfile.csv
foreach($s in $servers)
{
$testar = Test-Connection -Cn $s -BufferSize 16 -Count 1 -ea 0 -quiet
Write-Output "$s;$testar" | Out-File outfile.csv -Append
}

Outfile.csv

computer;connect
computer1;True
computer2;True
computer3;False
computer4;True