1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    * 
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.math.stat.descriptive.moment;
18  
19  import junit.framework.Test;
20  import junit.framework.TestSuite;
21  
22  import org.apache.commons.math.stat.descriptive.StorelessUnivariateStatisticAbstractTest;
23  import org.apache.commons.math.stat.descriptive.UnivariateStatistic;
24  
25  /**
26   * Test cases for the {@link UnivariateStatistic} class.
27   * 
28   * @version $Revision: 762087 $ $Date: 2009-04-05 10:20:18 -0400 (Sun, 05 Apr 2009) $
29   */
30  public class SkewnessTest extends StorelessUnivariateStatisticAbstractTest{
31  
32      protected Skewness stat;
33      
34      /**
35       * @param name
36       */
37      public SkewnessTest(String name) {
38          super(name);
39      }
40  
41      /**
42       * {@inheritDoc}
43       */
44      @Override
45      public UnivariateStatistic getUnivariateStatistic() {
46          return new Skewness();
47      }
48  
49      public static Test suite() {
50          TestSuite suite = new TestSuite(SkewnessTest.class);
51          suite.setName("Skewness Tests");
52          return suite;
53      }
54      
55      /**
56       * {@inheritDoc}
57       */
58      @Override
59      public double expectedValue() {
60          return this.skew;
61      }
62      
63      /**
64       * Make sure Double.NaN is returned iff n < 3
65       *
66       */
67      public void testNaN() {
68          Skewness skew = new Skewness();
69          assertTrue(Double.isNaN(skew.getResult()));
70          skew.increment(1d);
71          assertTrue(Double.isNaN(skew.getResult()));
72          skew.increment(1d);
73          assertTrue(Double.isNaN(skew.getResult()));
74          skew.increment(1d);
75          assertFalse(Double.isNaN(skew.getResult()));      
76      }
77  
78  }