Runs the "BB Test" problem as described in Federrath et al 2010, ApJ, 713, 269, and tests for mass conservation.
The initial conditions include isothermal gas, with the gas having a constant small "external density" outside of the truncation radius. Within the truncation radius, the gas density has the following form:
\rho(\phi) = \rho_0 (1 + A \cos(2 \phi)),
where \rho is the gas density, \phi is the azimuthal angle in the spherical polar coordinate system, \rho_0 is the mean density and A is the (small) fluctuation amplitude. In addition, the gas rotates around the z-axis as a solid-body.
When the problem is left to run, the gas collapses into a disk, and sink particles form near the center, which accrete gas and merge together.
This test can be executed by running "ctest -R bb_test" in the build directory.
All the files required for running the test can be found in input/bb_test. See input/bb_test/README for further information.