1   /*
2    * Copyright 2003-2004 The Apache Software Foundation.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.apache.commons.math.stat.descriptive.moment;
17  
18  import junit.framework.Test;
19  import junit.framework.TestSuite;
20  
21  import org.apache.commons.math.stat.descriptive.StorelessUnivariateStatisticAbstractTest;
22  import org.apache.commons.math.stat.descriptive.UnivariateStatistic;
23  
24  /**
25   * Test cases for the {@link UnivariateStatistic} class.
26   * 
27   * @version $Revision: 155427 $ $Date: 2005-02-26 06:11:52 -0700 (Sat, 26 Feb 2005) $
28   */
29  public class SkewnessTest extends StorelessUnivariateStatisticAbstractTest{
30  
31      protected Skewness stat;
32      
33      /**
34       * @param name
35       */
36      public SkewnessTest(String name) {
37          super(name);
38      }
39  
40      /* (non-Javadoc)
41       * @see org.apache.commons.math.stat.descriptive.UnivariateStatisticAbstractTest#getUnivariateStatistic()
42       */
43      public UnivariateStatistic getUnivariateStatistic() {
44          return new Skewness();
45      }
46  
47      public static Test suite() {
48          TestSuite suite = new TestSuite(SkewnessTest.class);
49          suite.setName("Skewness Tests");
50          return suite;
51      }
52      
53      /* (non-Javadoc)
54       * @see org.apache.commons.math.stat.descriptive.UnivariateStatisticAbstractTest#expectedValue()
55       */
56      public double expectedValue() {
57          return this.skew;
58      }
59      
60      /**
61       * Make sure Double.NaN is returned iff n < 3
62       *
63       */
64      public void testNaN() {
65          Skewness skew = new Skewness();
66          assertTrue(Double.isNaN(skew.getResult()));
67          skew.increment(1d);
68          assertTrue(Double.isNaN(skew.getResult()));
69          skew.increment(1d);
70          assertTrue(Double.isNaN(skew.getResult()));
71          skew.increment(1d);
72          assertFalse(Double.isNaN(skew.getResult()));      
73      }
74  
75  }