Moodle scheduled task with mtrace convenient for unit tests

mtrace-in-task.php

class move_to_recycle_bin extends scheduled_task {

    /** @var string For unit testing only */
    protected $testmtracebuffer = '';

    /**
     * Outputs a line of text to the cron log.
     *
     * @param string $line Line of text
     */
    public function mtrace($line) {
        if (PHPUNIT_TEST) {
            $this->testmtracebuffer .= $line . "\n";
        } else {
            mtrace($line);
        }
    }

    /**
     * For unit testing only. Get the mtraced output, and clear it.
     *
     * @return string Mtraced output (since last call)
     */
    public function get_and_clear_test_mtrace_buffer() {
        if (!PHPUNIT_TEST) {
            throw new \coding_exception('Cannot be called except in unit test');
        }
        $result = $this->testmtracebuffer;
        $this->testmtracebuffer = '';
        return $result;
    }
}