Splitting the tests at http://blog.xiag.ru/2012/11/blog-post_15.html

gistfile1.php

public function test_event_repetition_isnt_allowed() {
    $el = new EventLimiter;
    $el->confirmAllowed("sms"); // Заметь, без ассёрта! Уже проверяли.
    $this->assertFalse($el->confirmAllowed("sms"));
}
//==========
class EventLimiter {
    private $count = 0;

    public function confirmAllowed($event) {
        $this->count++;
        return ($this->count < 1);
    }
}

//затем

public function test_two_different_events_in_a_row_are_allowed() {
    $el = new EventLimiter;
    $el->confirmAllowed("sms1");
    $this->assertTrue($el->confirmAllowed("sms2"));
}
//==========
class EventLimiter {
    private $counts = [];

    public function confirmAllowed($event) {
        if (!isset($this->counts[$event])) {
            $this->counts[$event] = 0;
        } // дописал сверху этот if

        // А потом *эффектно* поменял count на counts
    $this->counts[$event]++;
        return ($this->counts[$event] < 1);
    }
}

//тепепь можно добавить в конструктор лимит

public function test_events_repetionion_limit_is_set_on_construction() {
    $el = new EventLimiter(2);
    $el->confirmAllowed("sms");
    $this->assertTrue($el->confirmAllowed("sms"));
    $this->assertFalse($el->confirmAllowed("sms"));
}
//==========
class EventLimiter {
    private $limit;
    private $counts = [];

    public function __construct($limit) {
        $this->limit = $limit ?: 1;
    }

    public function confirmAllowed($event) {
        if (!isset($this->counts[$event])) {
            $this->counts[$event] = 0;
        }

    $this->counts[$event]++;
        return ($this->counts[$event] < $this->limit);
        // опять же *эффектно* меняем 1 на $this->limit
    }
}