//=============================================================================
// Copyright 2006-2010 Daniel W. Dyer
//
// Licensed 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.uncommons.watchmaker.framework.operators;

import java.util.Arrays;
import java.util.List;
import org.testng.annotations.Test;
import org.uncommons.maths.binary.BitString;
import org.uncommons.maths.random.Probability;
import org.uncommons.watchmaker.framework.EvolutionaryOperator;
import org.uncommons.watchmaker.framework.FrameworkTestUtils;

/**
 * Unit test for mutation of bit strings.
 * @author Daniel Dyer
 */
public class BitStringMutationTest
{
    /**
     * Ensures that mutation occurs correctly.  Because of the random
     * aspect we can't actually make many assertions.  This just ensures
     * that there are no unexpected exceptions and that the length of
     * the bit strings remains as expected.
     */
    @Test
    public void testRandomMutation()
    {
        EvolutionaryOperator<BitString> mutation = new BitStringMutation(Probability.EVENS);
        BitString original = new BitString("111100101");
        List<BitString> population = Arrays.asList(original);
        for (int i = 0; i < 20; i++) // Perform several iterations to get different mutations.
        {
            population = mutation.apply(population, FrameworkTestUtils.getRNG());
            BitString mutated = population.get(0);
            assert mutated.getLength() == 9 : "Mutated bit string changed length.";
        }
    }


    /**
     * Ensures that mutation occurs correctly.  Uses a probability of 1 to
     * make the outcome predictable (all bits will be flipped).
     */
    @Test
    public void testSingleBitMutation()
    {
        BitString original = new BitString("111100101");
        EvolutionaryOperator<BitString> mutation = new BitStringMutation(Probability.ONE);                                                                         
        List<BitString> population = Arrays.asList(original);
        population = mutation.apply(population, FrameworkTestUtils.getRNG());
        BitString mutated = population.get(0);
        assert !mutated.equals(original) : "Mutation should be different from original.";
        assert mutated.getLength() == 9 : "Mutated bit string changed length.";
        int set = mutated.countSetBits();
        int unset = mutated.countUnsetBits();
        assert set == 5 || set == 7 : "Mutated bit string has wrong number of 1s: " + set;
        assert unset == 2 || unset == 4 : "Mutated bit string has wrong number of 0s: " + unset;
    }
}