Create (partial) backup of local MongoDB database

If one is developing some web application that uses a MongoDB database and one wants to demonstrate the application one might need some exemplary test data. This data needs to be created beforehand and it might be necessary to whipe the database between the creation of the test data and the demo. Or one might want to check the data into some version control systems for other developers to use this data to explore the application. The problem now is that one might have the data on a locally running MongoDB and wants to share this data with others or back it up for later uasge. Also one might only want to create a backup of ceratin parts of the database, like for example only of the test users, but no the test content createt for those users. It would be a very lengthy process to delete all the content by hand and then backup the whole database