001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     * 
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     * 
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.math.stat.descriptive.moment;
018    
019    import junit.framework.Test;
020    import junit.framework.TestSuite;
021    
022    import org.apache.commons.math.stat.descriptive.StorelessUnivariateStatisticAbstractTest;
023    import org.apache.commons.math.stat.descriptive.UnivariateStatistic;
024    
025    /**
026     * Test cases for the {@link UnivariateStatistic} class.
027     * 
028     * @version $Revision: 762087 $ $Date: 2009-04-05 10:20:18 -0400 (Sun, 05 Apr 2009) $
029     */
030    public class SkewnessTest extends StorelessUnivariateStatisticAbstractTest{
031    
032        protected Skewness stat;
033        
034        /**
035         * @param name
036         */
037        public SkewnessTest(String name) {
038            super(name);
039        }
040    
041        /**
042         * {@inheritDoc}
043         */
044        @Override
045        public UnivariateStatistic getUnivariateStatistic() {
046            return new Skewness();
047        }
048    
049        public static Test suite() {
050            TestSuite suite = new TestSuite(SkewnessTest.class);
051            suite.setName("Skewness Tests");
052            return suite;
053        }
054        
055        /**
056         * {@inheritDoc}
057         */
058        @Override
059        public double expectedValue() {
060            return this.skew;
061        }
062        
063        /**
064         * Make sure Double.NaN is returned iff n < 3
065         *
066         */
067        public void testNaN() {
068            Skewness skew = new Skewness();
069            assertTrue(Double.isNaN(skew.getResult()));
070            skew.increment(1d);
071            assertTrue(Double.isNaN(skew.getResult()));
072            skew.increment(1d);
073            assertTrue(Double.isNaN(skew.getResult()));
074            skew.increment(1d);
075            assertFalse(Double.isNaN(skew.getResult()));      
076        }
077    
078    }