tests/phpunit/includes/libs/RunningStatTest.php

   1 <?php
   2 /**
   3  * PHP Unit tests for RunningStat class.
   4  * @covers RunningStat
   5  */
   6 class RunningStatTest extends MediaWikiTestCase {
   7
   8         public $points = array(
   9                 49.7168, 74.3804,  7.0115, 96.5769, 34.9458,
  10                 36.9947, 33.8926, 89.0774, 23.7745, 73.5154,
  11                 86.1322, 53.2124, 16.2046, 73.5130, 10.4209,
  12                 42.7299, 49.3330, 47.0215, 34.9950, 18.2914,
  13         );
  14
  15         /**
  16          * Verify that the statistical moments and extrema computed by RunningStat
  17          * match expected values.
  18          * @covers RunningStat::push
  19          * @covers RunningStat::count
  20          * @covers RunningStat::getMean
  21          * @covers RunningStat::getVariance
  22          * @covers RunningStat::getStdDev
  23          */
  24         public function testRunningStatAccuracy() {
  25                 $rstat = new RunningStat();
  26                 foreach( $this->points as $point ) {
  27                         $rstat->push( $point );
  28                 }
  29
  30                 $mean = array_sum( $this->points ) / count( $this->points );
  31                 $variance = array_sum( array_map( function ( $x ) use ( $mean ) {
  32                         return pow( $mean - $x, 2 );
  33                 }, $this->points ) ) / ( count( $rstat ) - 1 );
  34                 $stddev = sqrt( $variance );
  35
  36                 $this->assertEquals( count( $rstat ), count( $this->points ) );
  37                 $this->assertEquals( $rstat->min, min( $this->points ) );
  38                 $this->assertEquals( $rstat->max, max( $this->points ) );
  39                 $this->assertEquals( $rstat->getMean(), $mean );
  40                 $this->assertEquals( $rstat->getVariance(), $variance );
  41                 $this->assertEquals( $rstat->getStdDev(), $stddev );
  42         }
  43
  44         /**
  45          * When one RunningStat instance is merged into another, the state of the
  46          * target RunningInstance should have the state that it would have had if
  47          * all the data had been accumulated by it alone.
  48          * @covers RunningStat::merge
  49          * @covers RunningStat::count
  50          */
  51         public function testRunningStatMerge() {
  52                 $expected = new RunningStat();
  53
  54                 foreach( $this->points as $point ) {
  55                         $expected->push( $point );
  56                 }
  57
  58                 // Split the data into two sets
  59                 $sets = array_chunk( $this->points, floor( count( $this->points ) / 2 ) );
  60
  61                 // Accumulate the first half into one RunningStat object
  62                 $first = new RunningStat();
  63                 foreach( $sets[0] as $point ) {
  64                         $first->push( $point );
  65                 }
  66
  67                 // Accumulate the second half into another RunningStat object
  68                 $second = new RunningStat();
  69                 foreach( $sets[1] as $point ) {
  70                         $second->push( $point );
  71                 }
  72
  73                 // Merge the second RunningStat object into the first
  74                 $first->merge( $second );
  75
  76                 $this->assertEquals( count( $first ), count( $this->points ) );
  77                 $this->assertEquals( $first, $expected );
  78         }
  79 }