I am a beginner at RaspberryPi programing so I hope the question doesn’t sound dumb. I would like to test a communication between two bluetooh modules in SPP mode. Is it possible to connect them both to TxD and RxD pins and test the Bluetooth connection this way?
Short answer: no, it's not enough to just connect Rx and Tx to MCU, as the modules do not know who to send messages to and who to receive from.
Assuming you mean HC-05/HC-06 bluetooth modules, apart from Rx and Tx pins you should power them via GND and VCC pins, and after powering up, you pair them and establish a link between them (A master module would require switching to AT mode for that, which, as I know, requires a KEY pin to be controlled as well). From this point what you send to one module's Tx would appear on another module's Rx and vica-verca.