Here is how to test Arduino + Xbee with a Mac. To test XBee-connected Arduino, you need a USB Explorer (USB-XBee adaptor), XBee-shield for Arduino, and two XBees.

1. Insert the first XBee chip in USB Explorer
2. Connect the USB Explorer to Mac A
3. Start XBeeConfigTool (from Funnel package)
4. Configure the first XBee chip (e.g. Network ID: 1234, MY ID: 1)
5. Remove the USB Explorer from the Mac A
6. Remove the first XBee chip and insert it in XBee shield
7. Insert the second XBee chip in the USB Explorer
8. Connect the USB Explorer to the Mac A
9. Start XBeeConfigTool
10. Configure the second XBee chip (e.g. Network ID: 1234, MY ID: 0)
11. Remove the USB Explorer from the Mac A
12. Insert the XBee shield on Arduino Uno
13. Move two jumpers to USB side
14. Connect the Arduino Uno to Mac B
15. Start Arduino.app on the Mac B
16. Open Example > Communication > PhysicalPixel sketch
17. Upload the sketch to the Arduino Uno
18. Test the Arduino Uno by opening Serial Monitor and type ‘H’ (to turn LED on) and ‘L’ (to turn LED off)
19. Exit Arduino.app
20. Remove the Arduino Uno from the Mac B
21. Move two jumpers to XBee side
22. Power the Arduino Uno (by connecting with USB port of the Mac B)
23. Connect the USB Explorer (with the second XBee chip) to the Mac A
24. On Terminal.app on Mac A, do echo ‘H’ > /dev/cu.usbserial-A600ezs6 (or similar) to turn LED on remotely and do ‘L’ to turn LED off

I used a couple of Macs (A and B) but you should be okay with a single Mac.