Using VMware/Virtual box to simulate a cluster of nodes, but actually using a single machine

I am developing a webapp using Cassandra database which works on a multi-nodes cluster. But I don't have multiple machines to create a cluster while development. How do I create a cluster using the resources of a single machine? Can I do this by creating VMware or Virtual box instances that are connected to each other to form cluster?

Yes. If the computer can handle it, you can run multiple virtual machines simultaneously. The easiest configuration would be to have them all use bridged network adapters, so they are on the same subnet as the host.