for j := 0.0; j < mass; j += mass * 0.099 {
			mud.setTrackMass(j)
			l, u, ok := mud.approxInvCumulativeSum()
			inv, ok2 := mud.invCumulativeSum(j)
			if !ok || !ok2 {
				t.Fatalf("inverse cumulative sum failed: approx %v, exact %v", ok, ok2)
			}
			if !(l <= inv && inv < u) {
				t.Fatalf("inverse(%g) = %g, not ∈ [%g, %g)", j, inv, l, u)
			}
		}
	}
}

func TestMUDTracking(t *testing.T) {