Most DNS tools (like dig and nslookup) perform IP lookups against DNS servers, ignoring /etc/hosts entries. Luckily, OS X provides the dscacheutil command to perfom a number of functions including checking local host entries. Below is an example that I used to verify the hostname/IP address combo that my system had registered in /etc/hosts.
While MongoDB can be managed well from the command line, it is often nice to have a GUI app to get an overview of a collection, server status, or to easily interact with other OS X apps.