LinearDistributionNearbyRandomTest.java

/*
 * Copyright 2014 Red Hat, Inc. and/or its affiliates.
 *
 * 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.optaplanner.core.impl.heuristic.selector.common.nearby;

import java.util.Random;

import org.junit.Test;

import static org.junit.Assert.*;
import static org.mockito.Mockito.*;

public class LinearDistributionNearbyRandomTest {

    @Test(expected = IllegalArgumentException.class)
    public void sizeMaximumTooLow() {
        NearbyRandom nearbyRandom = new LinearDistributionNearbyRandom(-10);
    }

    @Test
    public void nextInt() {
        Random random = mock(Random.class);
        NearbyRandom nearbyRandom = new LinearDistributionNearbyRandom(100);

        when(random.nextDouble()).thenReturn(0.0);
        assertEquals(0, nearbyRandom.nextInt(random, 500));
        when(random.nextDouble()).thenReturn(2.0 / 100.0);
        assertEquals(1, nearbyRandom.nextInt(random, 500));
        when(random.nextDouble()).thenReturn(2.0 / 100.0 + 2.0 / 100.0 + 2.0 / 10000.0);
        assertEquals(2, nearbyRandom.nextInt(random, 500));
        when(random.nextDouble()).thenReturn(2.0 / 100.0 + 2.0 / 100.0 + 2.0 / 10000.0 + 2.0 / 100.0 + 4.0 / 10000.0);
        assertEquals(3, nearbyRandom.nextInt(random, 500));

        when(random.nextDouble()).thenReturn(0.0);
        assertEquals(0, nearbyRandom.nextInt(random, 10));
        when(random.nextDouble()).thenReturn(2.0 / 10.0);
        assertEquals(1, nearbyRandom.nextInt(random, 10));
    }

    @Test
    public void cornerCase() {
        Random random = mock(Random.class);
        NearbyRandom nearbyRandom = new LinearDistributionNearbyRandom(100);

        when(random.nextDouble()).thenReturn(Math.nextAfter(1.0, Double.NEGATIVE_INFINITY));
        assertEquals(9, nearbyRandom.nextInt(random, 10));

        when(random.nextDouble()).thenReturn(Math.nextAfter(1.0, Double.NEGATIVE_INFINITY));
        assertEquals(99, nearbyRandom.nextInt(random, 500));
    }

}