EKF testing gaps

[dagar]

Overall test coverage is looking good, but there are still a number of gaping holes.

• airspeed_fusion.cpp 68.67% https://codecov.io/gh/PX4/ecl/src/master/EKF/airspeed_fusion.cpp
• drag_fusion.cpp 0% https://codecov.io/gh/PX4/ecl/src/master/EKF/drag_fusion.cpp
• mag_control.cpp 78.15% https://codecov.io/gh/PX4/ecl/src/master/EKF/mag_control.cpp
  • explicitly test modes other than MAG_FUSE_TYPE_AUTO
• optflow_fusion.cpp 0% https://codecov.io/gh/PX4/ecl/src/master/EKF/optflow_fusion.cpp
• sideslip_fusion.cpp 0% https://codecov.io/gh/PX4/ecl/src/master/EKF/sideslip_fusion.cpp

[dagar]

Testing the different height modes is another missing piece.

[bresch]

Good to know, thanks @dagar . I'll add a task for myself to remember adding basic coverage of those functions. Also, if anyone else is interested to do it, he/she's more than welcome!