Asynchronous drivers can be tested at the basic level by setting up a login line to the serial ports. A good test is to see whether a user can log in on this line. To sufficiently test an asynchronous driver, however, all the I/O control functions must be tested, with many interrupts at high speed. A test involving a loopback serial cable and high data transfer rates can help determine the reliability of the driver. You can run uucp(1C) over the line to provide some exercise. However, because uucp performs its own error handling, verify that the driver is not reporting excessive numbers of errors to the uucp process.
These types of devices are usually STREAMS-based. See the STREAMS Programming Guide for more information.