test_magneticFieldWMMStepLag

Test that the magnetic field base class evaluates a time dependent model at the step midpoint.

The WMM field changes with the decimal year of the evaluation time. The spacecraft is at rest, so the extrapolation moves nothing and only the evaluation time of the model can change the field.

test_magneticFieldWMMStepLag.test_model_time_is_the_step_midpoint()

Verify the model is evaluated at the step midpoint when the extrapolation applies.

With the extrapolation the third update, at 20 s, evaluates the model at 15 s. This must equal the field of a run without extrapolation whose epoch is 5 s earlier, and differ from the field of a run without extrapolation at the same epoch, which evaluates at 20 s.