Test UART send and receive without a physical device
You can do a simple &quot;loopback&quot; test - connect your Tx output to your RX input - if all is well, you can talk to yourself.
EDIT
The loopback test only shows that your transmit/receive routines are working.  As @BeB00 comments, this does not test the baud rate settings, as most UARTs use the same clock for both transmit and receive.