/*
    * Licensed to the Hipparchus project under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The Hipparchus project licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.hipparchus.optim.nonlinear.vector.constrained;
  
  import org.hipparchus.linear.MatrixUtils;
  import org.hipparchus.linear.RealMatrix;
  import org.hipparchus.linear.RealVector;
  import org.junit.Assert;
  import org.junit.Test;
  
  public class TwiceDifferentiableFunctionTest {
  
      @Test
      public void testValue() {
          // GIVEN
          final double[] x = new double[] { 2. };
          final TestTwiceDifferentiableFunction function = new TestTwiceDifferentiableFunction();
          // WHEN
          final double actualValue = function.value(x);
          // THEN
          final double expectedValueElement = x[0];
          Assert.assertEquals(expectedValueElement, actualValue, 0);
      }
  
      @Test
      public void testGradient() {
          // GIVEN
          final double[] x = new double[] { 2. };
          final TestTwiceDifferentiableFunction function = new TestTwiceDifferentiableFunction();
          // WHEN
          final RealVector actualGradient = function.gradient(x);
          // THEN
          final double expectedValueElement = 1.;
          Assert.assertEquals(expectedValueElement, actualGradient.getEntry(0), 0);
      }
  
      @Test
      public void testHessian() {
          // GIVEN
          final double[] x = new double[] { 2. };
          final TestTwiceDifferentiableFunction function = new TestTwiceDifferentiableFunction();
          // WHEN
          final RealMatrix actualGradient = function.hessian(x);
          // THEN
          final double expectedValueElement = 0.;
          Assert.assertEquals(expectedValueElement, actualGradient.getEntry(0, 0), 0);
      }
  
      private static class TestTwiceDifferentiableFunction extends TwiceDifferentiableFunction {
  
          @Override
          public int dim() {
              return 1;
          }
  
          @Override
          public double value(RealVector x) {
              return x.getEntry(0);
          }
  
          @Override
          public RealVector gradient(RealVector x) {
              return MatrixUtils.createRealVector(new double[] { 1. });
          }
  
          @Override
          public RealMatrix hessian(RealVector x) {
              return MatrixUtils.createRealMatrix(1, 1);
          }
  
      }
  
  }