A method is provided for identifying a data transfer mismatch between a sender and a
receiver from among units of a
software simulator of a hardware processor. The simulator runs the plurality of the units which communicate with each other via First-In First-Outs (FIFOs). The method counts amounts of data the sender writes to the FIFOs and the
receiver reads from the FIFOs for a given data transfer. The method avoids blocking during FIFO reading and writing operations by (i) reading
dummy data by the
receiver, even if the FIFOs are empty, when the receiver tries reading from the FIFOs, and (ii) discarding written data if the FIFOs are full, when the sender tries writing to the FIFOs. The method identifies mismatches in the amount of data the sender writes to the FIFOs versus the amount of data the receiver reads from the FIFOs for the given data transfer.