Specifically need to add test with contact in which both objects have friction directions specified. Also, it seems that friction direction for the second object in a collision is not ever considered in gazebo (see ODEPhysics.cc:906).
So I gather things should work when two bodies collide and only one of them has fdir1 set? What is the expected result when both have fdir1 set? I´m currently experiencing issues with fdir1 as described on Gazebo Q/A.
It's been almost a year, and I haven't made any progress on the expected behavior for two surfaces that have specified friction directions. I'm going to mark this On hold until we make further progress. Feel free to continue discussion and/or vote for this issue.