There are projects which provide daemons needing to be able to create, modify and delete Unix users. Or just switch user ids to interact with the system e.g. a user space file server. To be able to test that you need the privilege to modify the passwd and groups file. With nss_wrapper it is possible to define your own passwd and groups file which will be used by software to act correctly while under test. If you have a client and server under test they normally use functions to resolve network names to addresses (dns) or vice versa. The nss_wrappers allow you to create a hosts file to setup name resolution for the addresses you use with socket_wrapper. - Provides information for user and group accounts. - Network name resolution using a hosts file. - Loading and testing of NSS modules.