message: testfunctions documentation
diff: // http://opensource.org/licenses/MIT>, at your option. This file may not be
  // copied, modified, or distributed except according to those terms.
  -//! TODO Documentation
  +//! # Test functions
  +//!
  +//! Test functions to test optimization algorithms.
  +//!
  +//! * Rosenbrock
  +//! * Sphere
  use std::iter::Sum;
  use ndarray::{Array1, Array2};
  