There are unused methods on the GridFS API, which suggests they are not tested:

• public DBCursor getFileList(final DBObject query)
• public DBCursor getFileList(final DBObject query, final DBObject sort)
• public GridFSInputFile createFile(final InputStream in)

In addition, the GridFSFile class is referenced in any test classes at all - granted it is an abstract class, but I would expect it to be tested as a side effect of testing the GridFS functionality.

There are also untested methods on GridFSInputFile:

• public int saveChunks()