fails:Encoding::Converter#replacement returns '?' in US-ASCII when the destination encoding is not UTF-8
fails:Encoding::Converter#replacement returns u{fffd} when the destination encoding is UTF-8
fails:Encoding::Converter#replacement= accepts a String argument
fails:Encoding::Converter#replacement= accepts a String argument of arbitrary length
fails:Encoding::Converter#replacement= raises an TypeError if assigned a non-String argument
fails:Encoding::Converter#replacement= sets #replacement
fails:Encoding::Converter#replacement= raises an UndefinedConversionError is the argument cannot be converted into the destination encoding
fails:Encoding::Converter#replacement= does not change the replacement character if the argument cannot be converted into the destination encoding
