CakePHPでBASIC認証をするComponent ref: http://qiita.com/kazurof/items/94a07b672f062e2db568

BasicAuthComponent.php

<?php
class BasicAuthComponent extends Component {
    public function startup(Controller $controller) {
        if (!isset($_SERVER['PHP_AUTH_USER']) || !isset($_SERVER['PHP_AUTH_PW']) || $_SERVER['PHP_AUTH_USER'] !== BASIC_USERID || $_SERVER['PHP_AUTH_PW'] !== BASIC_PASSWD) {
            $controller->autoRender = false;
            $controller->response->header('WWW-Authenticate: Basic realm="Please enter your ID and password"');
            $controller->response->statusCode(401);
            $controller->response->send();
            $this->_stop("id / password Required");
        }
    }
}

BasicAuthComponentTest.php

<?php
App::uses('ComponentCollection', 'Controller');
App::uses('Component', 'Controller');
App::uses('BasicAuthComponent', 'Controller/Component');
App::uses('Controller', 'Controller');
App::uses('CakeRequest', 'Network');
App::uses('CakeResponse', 'Network');

class BasicAuthComponentTest extends CakeTestCase {

    public $fixtures = [
    ];

    public $response = null;
    public $controller = null;
    public $component = null;

    public function setUp() {
        parent::setUp();

        $this->response = $this->getMockBuilder('CakeResponse')->setMethods(['header', 'statusCode', 'send'])->getMock();
        $this->controller = new Controller(new CakeRequest(), $this->response);

        $this->component = $this->getMockBuilder('BasicAuthComponent')->setConstructorArgs([new ComponentCollection()])
            ->setMethods(['_stop'])
            ->getMock();
    }

    public function tearDown() {
        parent::tearDown();
    }

    public function test_ログインが成功する() {
        $_SERVER['PHP_AUTH_USER'] = "test";
        $_SERVER['PHP_AUTH_PW'] = "pass";

        $this->response->expects($this->never())->method('header');
        $this->response->expects($this->never())->method('statusCode');
        $this->response->expects($this->never())->method('send');
        $this->component->expects($this->never())->method('_stop');

        $this->component->initialize($this->controller);
        $this->component->startup($this->controller);
        $this->assertTrue($this->controller->autoRender);
    }

    public function test_ログインが失敗する_id_passが正しくない() {
        $_SERVER['PHP_AUTH_USER'] = "nantoka";
        $_SERVER['PHP_AUTH_PW'] = "kantoka";

        $this->response->expects($this->once())->method('header')->with('WWW-Authenticate: Basic realm="Please enter your ID and password"');
        $this->response->expects($this->once())->method('statusCode')->with(401);
        $this->response->expects($this->once())->method('send')->with();
        $this->component->expects($this->once())->method('_stop')->with("id / password Required");

        $this->component->initialize($this->controller);
        $this->component->startup($this->controller);
        $this->assertFalse($this->controller->autoRender);
    }
}