If you want to create a test for a GRASS 7 module which exports a raster output, you will need extra steps. There isa great chance that your GRASS 7 installation will be different from the Travis-Ci environment (for the moment, it is provided by [osgeo4travis archive]( and it is based on GRASS 7.0.2). It means that your raster hashes will be different from the ones produced in Travis-Ci (GRASS adds a metadata which contains the GRASS version in the GTiff).
Here are a few instructions (for Debian based GNU/Linux distributions) to assure you use the same version of GRASS than in Travis-Ci:
* Install osgeo4travis binaries into your home directory:
`curl -L https://github.com/opengisch/osgeo4travis/archive/qt4bin.tar.gz | tar -xzC ${HOME} --strip-components=1`
* Modify the grass70 script which incorporates a hardlink to /home/travis:
From now, you will be using osgeo4travis GRASS 7 installation in QGIS Processing and you can proceed with the above method to easily produce unit tests.