/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF 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
    *
    *      http://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.apache.commons.math4.transform;
  
  import java.util.function.DoubleUnaryOperator;
  
  import org.junit.Assert;
  import org.junit.Test;
  
  import org.apache.commons.math3.analysis.function.Sin;
  
  import static org.junit.jupiter.api.Assertions.assertThrows;
  
  /**
   * Tests for {@link TransformUtils}.
   */
  public class TransformUtilsTest {
  
      private static final Sin SIN_FUNCTION = new Sin();
      private static final DoubleUnaryOperator SIN = x -> SIN_FUNCTION.value(x);
  
      @Test
      public void testSampleWrongBounds() {
          assertThrows(TransformException.class, () ->
                  TransformUtils.sample(SIN, Math.PI, 0.0, 10));
      }
  
      @Test
      public void testSampleNegativeNumberOfPoints() {
          assertThrows(TransformException.class, () ->
                  TransformUtils.sample(SIN, 0.0, Math.PI, -1));
      }
  
      @Test
      public void testSampleNullNumberOfPoints() {
          assertThrows(TransformException.class, () ->
                  TransformUtils.sample(SIN, 0.0, Math.PI, 0));
      }
  
      @Test
      public void testSample() {
          final int n = 11;
          final double min = 0.0;
          final double max = Math.PI;
          final double[] actual = TransformUtils.sample(SIN, min, max, n);
          for (int i = 0; i < n; i++) {
              final double x = min + (max - min) / n * i;
              Assert.assertEquals("x = " + x, Math.sin(x), actual[i], 1e-15);
          }
      }
  
  }