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.

WWW: https://cwrap.org/nss_wrapper.html