A printer for PHPUnit that includes top 10 slowest tests in results. With `--verbose` it will show the top 10 slowest test methods.

TimerPrinter.php

<?php
namespace App\TestSuite;

use Cake\Collection\Collection;
use PHPUnit\Framework\Test;
use PHPUnit\Util\Test as TestUtil;
use PHPUnit\TextUI\ResultPrinter;

class TimerPrinter extends ResultPrinter
{
    /**
     * @var array
     */
    public static $timers = [];

    /**
     * @param Test $test Test
     * @param float $time Time in microseconds
     */
    public function endTest(Test $test, $time)
    {
        $fullTestName = TestUtil::describe($test);
        list($testName, $method) = explode('::', $fullTestName);

        self::$timers[] = [
            'test' => $testName,
            'method' => $method,
            'time' => $time,
        ];

        parent::endTest($test, $time);
    }

    /**
     * @param \PHPUnit\Framework\TestResult $result TestResult
     * @return void
     */
    public function printFooter(\PHPUnit\Framework\TestResult $result)
    {
        $timers = collection(self::$timers)
            ->sortBy('time', SORT_DESC, SORT_NUMERIC)
            ->take(10)
            ->groupBy('test');

        if ($this->verbose) {
            $this->writeTimersVerbose($timers);
        } else {
            $this->writeTimers($timers);
        }

        parent::printFooter($result);
    }

    /**
     * @param Collection $timers Timers
     */
    private function writeTimersVerbose(Collection $timers)
    {
        foreach ($timers as $testClassName => $methodTimers) {
            $this->write($testClassName);
            $this->writeNewLine();
            foreach ($methodTimers as $methodResults) {
                $timeAsString = number_format($methodResults['time'] * 1000) . 'ms';
                $classParts = namespaceSplit($methodResults['test']);
                $methodName = substr($classParts[1] . '::' . $methodResults['method'], 0, 70);

                $pad = 78 - (strlen($methodName) + strlen($timeAsString));

                $this->write('  ' . $methodName . str_pad('', $pad, '.') . $timeAsString);
                $this->writeNewLine();
            }
        }

        $this->writeNewLine();
    }

    /**
     * @param Collection $timers Timers
     */
    private function writeTimers(Collection $timers)
    {
        foreach ($timers as $testClassName => $methodTimers) {
            $totalTime = (new Collection($methodTimers))->sumOf('time');

            $timeAsString = number_format($totalTime * 1000) . 'ms';
            $testClassName = substr($testClassName, 0, 70);
            $pad = 80 - (strlen($testClassName) + strlen($timeAsString));

            $this->write($testClassName . str_pad('', $pad, '.') . $timeAsString);
            $this->writeNewLine();
        }

        $this->writeNewLine();
    }
}