src/test/java/org/apache/commons/math3/genetics/OnePointCrossoverTest.java

/*
 * 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,
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 * See the License for the specific language governing permissions and
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package org.apache.commons.math3.genetics;

import org.junit.Assert;
import org.junit.Test;

public class OnePointCrossoverTest {

    @Test
    public void testCrossover() {
        @SuppressWarnings("boxing")
        Integer[] p1 = new Integer[] {1,0,1,0,0,1,0,1,1};
        @SuppressWarnings("boxing")
        Integer[] p2 = new Integer[] {0,1,1,0,1,0,1,1,1};

        BinaryChromosome p1c = new DummyBinaryChromosome(p1);
        BinaryChromosome p2c = new DummyBinaryChromosome(p2);

        OnePointCrossover<Integer> opc = new OnePointCrossover<Integer>();

        // how to test a stochastic method?
        for (int i=0; i<20; i++) {
            ChromosomePair pair = opc.crossover(p1c,p2c);

            Integer[] c1 = new Integer[p1.length];
            Integer[] c2 = new Integer[p2.length];

            c1 = ((BinaryChromosome) pair.getFirst()).getRepresentation().toArray(c1);
            c2 = ((BinaryChromosome) pair.getSecond()).getRepresentation().toArray(c2);

            // first and last values will be the same
            Assert.assertEquals(p1[0],  c1[0]);
            Assert.assertEquals(p2[0], c2[0]);
            Assert.assertEquals(p1[p1.length-1], c1[c1.length-1]);
            Assert.assertEquals(p2[p2.length-1], c2[c2.length-1]);
            // moreover, in the above setting, the 2nd, 3rd and 7th values will be the same
            Assert.assertEquals(p1[2], c1[2]);
            Assert.assertEquals(p2[2], c2[2]);
            Assert.assertEquals(p1[3], c1[3]);
            Assert.assertEquals(p2[3], c2[3]);
            Assert.assertEquals(p1[7], c1[7]);
            Assert.assertEquals(p2[7], c2[7]);
        }
    }

}