commons-rng-sampling/src/test/java/org/apache/commons/rng/sampling/distribution/InverseTransformParetoSamplerTest.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
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 * 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.rng.sampling.distribution;

import org.apache.commons.rng.RestorableUniformRandomProvider;
import org.apache.commons.rng.UniformRandomProvider;
import org.apache.commons.rng.sampling.RandomAssert;
import org.apache.commons.rng.simple.RandomSource;
import org.junit.Test;

/**
 * Test for the {@link InverseTransformParetoSampler}. The tests hit edge cases for the sampler.
 */
public class InverseTransformParetoSamplerTest {
    /**
     * Test the constructor with a bad scale.
     */
    @Test(expected = IllegalArgumentException.class)
    public void testConstructorThrowsWithZeroScale() {
        final RestorableUniformRandomProvider rng =
            RandomSource.create(RandomSource.SPLIT_MIX_64);
        final double scale = 0;
        final double shape = 1;
        InverseTransformParetoSampler.of(rng, scale, shape);
    }

    /**
     * Test the constructor with a bad shape.
     */
    @Test(expected = IllegalArgumentException.class)
    public void testConstructorThrowsWithZeroShape() {
        final RestorableUniformRandomProvider rng =
            RandomSource.create(RandomSource.SPLIT_MIX_64);
        final double scale = 1;
        final double shape = 0;
        InverseTransformParetoSampler.of(rng, scale, shape);
    }

    /**
     * Test the SharedStateSampler implementation.
     */
    @Test
    public void testSharedStateSampler() {
        final UniformRandomProvider rng1 = RandomSource.create(RandomSource.SPLIT_MIX_64, 0L);
        final UniformRandomProvider rng2 = RandomSource.create(RandomSource.SPLIT_MIX_64, 0L);
        final double scale = 1.23;
        final double shape = 4.56;
        final SharedStateContinuousSampler sampler1 =
            InverseTransformParetoSampler.of(rng1, scale, shape);
        final SharedStateContinuousSampler sampler2 = sampler1.withUniformRandomProvider(rng2);
        RandomAssert.assertProduceSameSequence(sampler1, sampler2);
    }
}