EDIT

<?php

// using namespace to allow for better sorting of test classes in the results

namespace test\phpunit\unit;

use PHPUnit\Framework\TestCase;

// these includes require <includePath>../..</includePath> to be set in phpUnit.xml

include 'includes/common.inc';

include 'cdm_api/commons.php';

/**

 * test to test if phpUnit is ok

 * @author a.kohlbecker

 *

 */

class StatisticalValuesTest extends TestCase {

  function new_statistical_value($value = null){

    $stat_val = new \stdClass(); // need to use the root namespace

    $stat_val->_value = $value;

    return $stat_val;

  }

  function create_statistical_values($typicalLowerBoundary = null, $typicalUpperrBoundary = null, $average  = null, $sampleSize = null){

    $stat_vals = statistical_values_array();

    $stat_vals['TypicalLowerBoundary'] = $this->new_statistical_value($typicalLowerBoundary);

    $stat_vals['TypicalUpperBoundary'] = $this->new_statistical_value($typicalUpperrBoundary);

    $stat_vals['SampleSize'] = $this->new_statistical_value($sampleSize);

    $stat_vals['Average'] = $this->new_statistical_value($average);

    return $stat_vals;

  }

  function html2text($html){

    return  html_entity_decode(strip_tags($html), ENT_COMPAT, 'utf-8');

  }

  function test_statistical_values() {

    $stat_vals = $this->create_statistical_values(0.123457,  0.123456, 0.123456523847, 5);

    $this->assertEquals('0.123457–0.123456[5;x̄=0.1234565]', $this->html2text(statistical_values($stat_vals)));

    $stat_vals = $this->create_statistical_values(12.23,  14.2, 13.2231423, 15);

    $this->assertEquals('12.23–14.2[15;x̄=13.2]', $this->html2text(statistical_values($stat_vals)));

    $stat_vals = $this->create_statistical_values(4,  6, 5, 2);

    $this->assertEquals('4–6[2;x̄=5]', $this->html2text(statistical_values($stat_vals)));

    $stat_vals = $this->create_statistical_values(4,  6, 5.0000, 2);

    $this->assertEquals('4–6[2;x̄=5]', $this->html2text(statistical_values($stat_vals)));

    $stat_vals = $this->create_statistical_values(6.3467,  6.3482, 6.347034915, 20);

    $this->assertEquals('6.3467–6.3482[20;x̄=6.34703]', $this->html2text(statistical_values($stat_vals)));

    $stat_vals = $this->create_statistical_values(0.00000001,  1, (1 - 0.00000001) / 2, 20);

    $this->assertEquals('1.0E-8–1[20;x̄=0.5]', $this->html2text(statistical_values($stat_vals)));

  }

}