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      1 /*
      2  * Copyright (C) 2011 The Android Open Source Project
      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 com.android.tradefed.util;
     17 
     18 import junit.framework.TestCase;
     19 
     20 /**
     21  * Unit tests for {@link SimpleStats}
     22  */
     23 public class SimpleStatsTest extends TestCase {
     24     private SimpleStats mStats = null;
     25 
     26     /**
     27      * {@inheritDoc}
     28      */
     29     @Override
     30     public void setUp() throws Exception {
     31         mStats = new SimpleStats();
     32     }
     33 
     34     /**
     35      * Make sure that the class behaves as expected when the dataset is empty
     36      */
     37     public void testStats_empty() {
     38         assertTrue(mStats.isEmpty());
     39         assertEquals(0, mStats.size());
     40         assertNull(mStats.mean());
     41         assertNull(mStats.median());
     42         assertNull(mStats.min());
     43         assertNull(mStats.max());
     44         assertNull(mStats.stdev());
     45     }
     46 
     47     /**
     48      * Make sure that the class behaves as expected with an even count of uniformly-distributed
     49      * measurements.
     50      * <p />
     51      * The even/odd distinction applies mainly to the median (which uses a different calculation
     52      * depending on whether the "center" element is unique or not).
     53      */
     54     public void testStats_evenCount() {
     55         // [1, 10]
     56         for (int i = 1; i <= 10; ++i) {
     57             mStats.add(i);
     58         }
     59         assertEquals(10, mStats.size());
     60         assertEquals(1, mStats.min(), 0.1);
     61         assertEquals(10, mStats.max(), 0.1);
     62         assertEquals(5.5, mStats.mean(), 0.1);
     63         assertEquals(5.5, mStats.median(), 0.1);
     64         assertEquals(2.872281, mStats.stdev(), 0.000001);
     65     }
     66 
     67     /**
     68      * Make sure that the class behaves as expected with an even count of uniformly-distributed
     69      * measurements.
     70      * <p />
     71      * The even/odd distinction applies mainly to the median (which uses a different calculation
     72      * depending on whether the "center" element is unique or not).
     73      */
     74     public void testStats_oddCount() {
     75         // [0, 10]
     76         for (int i = 0; i <= 10; ++i) {
     77             mStats.add(i);
     78         }
     79         assertEquals(11, mStats.size());
     80         assertEquals(0, mStats.min(), 0.1);
     81         assertEquals(10, mStats.max(), 0.1);
     82         assertEquals(5.0, mStats.mean(), 0.1);
     83         assertEquals(5.0, mStats.median(), 0.1);
     84         assertEquals(3.162278, mStats.stdev(), 0.000001);
     85     }
     86 
     87     /**
     88      * The skewed distribution will cause mean and median to diverge
     89      */
     90     public void testStats_skewedMedian() {
     91         for (int i = 1; i <= 5; ++i) {
     92             for (int j = 1; j <= i; ++j) {
     93                 mStats.add(i);
     94             }
     95         }
     96 
     97         // 1 + 2 + 3 + 4 + 5 = 15 elements
     98         assertEquals(15, mStats.size());
     99         assertEquals(1, mStats.min(), 0.1);
    100         assertEquals(5, mStats.max(), 0.1);
    101         // sum = 55, count = 15
    102         assertEquals(55.0 / 15.0, mStats.mean(), 0.1);
    103         assertEquals(4, mStats.median(), 0.1);
    104         assertEquals(1.247219, mStats.stdev(), 0.000001);
    105     }
    106 }
    107 
    108