This allows plain text passwords to be supplied in DSC configurations. Be aware it puts the password in plain text in c:\windows\system32\configuration\current.mof (and possibly other places)

gistfile1.ps1

$CfgData =@{
    AllNodes =@(
       @{
            NodeName = $Env:Computername;
            PSDscAllowPlainTextPassword = $true;
        }
    )
}

configuration TestFile {
    param ($Cred)

    node $env:computername {
        File Test {
            SourcePath = "\\server\share\test.txt"
            DestinationPath = "c:\dest\test.txt"
            Credential = $cred
        }
    }
}

TestFile -cred (get-credential) -configurationData $CfgData
Start-DSCConfiguration -path .\TestFile -ComputerName $Env:Computername | wait-job | receive-job