@Test
public void frobeniusNorm() {

  assertThat(
          MatrixUtils.frobeniusNorm(
              new DenseDoubleMatrix2D(
                  new double[][] {
                    {1, -1},
                    {2, 0}
                  })))
      .isEqualTo(Math.sqrt(1 * 1 + (-1) * (-1) + 2 * 2));
}