bootstrap.php

<?php

/**
 * Simple Magento integration test PHPUnit bootstrap
 */

chdir(__DIR__ . '/../..');

$mageFile = 'htdocs/app/Mage.php';
umask(0);
if (! $mageFile) {
    echo "Unable to locate app/Mage.php\n";
    exit(2);
}

// for mikey179/vfsStream
require_once 'vendor/autoload.php';
// bootstrap Magento
require_once $mageFile;
// mock response object that doesn't really send out anything
require_once __DIR__ . '/VinaiKopp/TestFramework/Controller/Response/Http.php';

/**
 * Reset and initialize the Magento runtime environment
 * 
 * @param string $configModelClass
 */
function resetMagento($configModelClass = null)
{
    Mage::reset();
    Mage::setIsDeveloperMode(true);
    $options = array();
    if ($configModelClass) $options['config_model'] = $configModelClass;
    Mage::app('admin', 'store', $options)
        ->setResponse(new VinaiKopp_TestFramework_Controller_Response_Http);

    // Fix error handler/Magento autoloader
    $handler = set_error_handler(function() {});
    set_error_handler(function($errno, $errstr, $errfile, $errline) use ($handler) {
        if (E_WARNING === $errno
            && 0 === strpos($errstr, 'include(')
            && substr($errfile, -19) == 'Varien/Autoload.php'
        ){
            return null;
        }
        call_user_func($handler, $errno, $errstr, $errfile, $errline);
    });
}

// initialize Magento runtime
resetMagento();

vinaikopp:TestFramework:Controller:Response:Http.php

<?php


class VinaiKopp_TestFramework_Controller_Response_Http extends Mage_Core_Controller_Response_Http
{
    protected $_headersSentFlag = false;

    public function canSendHeaders($throw = false)
    {
        if ($this->_headersSentFlag) {
            // Will trigger headers sent exception in testing context
            return parent::canSendHeaders($throw);
        }
        return true;
    }
    
    public function setHeadersSentFlag($flag)
    {
        $this->_headersSentFlag = (bool) $flag;
    }
    
    /**
     * Contains all parent logic except that the actual header sending is disabled.
     *
     * @return Mage_Core_Controller_Response_Http
     * @see Mage_Core_Controller_Response_Http::sendHeaders()
     * @see Zend_Controller_Response_Abstract::sendHeaders()
     */
    public function sendHeaders()
    {
        // From Mage_Core_Controller_Response_Http --------------------------

        if (!$this->canSendHeaders()) {
            Mage::log('HEADERS ALREADY SENT: ' . mageDebugBacktrace(true, true, true));
            return $this;
        }

        if (substr(php_sapi_name(), 0, 3) == 'cgi') {
            $statusSent = false;
            foreach ($this->_headersRaw as $i => $header) {
                if (stripos($header, 'status:') === 0) {
                    if ($statusSent) {
                        unset($this->_headersRaw[$i]);
                    } else {
                        $statusSent = true;
                    }
                }
            }
            foreach ($this->_headers as $i => $header) {
                if (strcasecmp($header['name'], 'status') === 0) {
                    if ($statusSent) {
                        unset($this->_headers[$i]);
                    } else {
                        $statusSent = true;
                    }
                }
            }
        }
        
        // End code from  Mage_Core_Controller_Response_Http --------------------------

        // From Zend_Controller_Response_Abstract --------------------------

        // Only check if we can send headers if we have headers to send
        if (count($this->_headersRaw) || count($this->_headers) || (200 != $this->_httpResponseCode)) {
            $this->canSendHeaders(true);
        } elseif (200 == $this->_httpResponseCode) {
            // Haven't changed the response code, and we have no headers
            return $this;
        }

        $httpCodeSent = false;

        foreach ($this->_headersRaw as $header) {
            if (!$httpCodeSent && $this->_httpResponseCode) {
                //header($header, true, $this->_httpResponseCode);
                $httpCodeSent = true;
            } else {
                //header($header);
            }
        }

        foreach ($this->_headers as $header) {
            if (!$httpCodeSent && $this->_httpResponseCode) {
                //header($header['name'] . ': ' . $header['value'], $header['replace'], $this->_httpResponseCode);
                $httpCodeSent = true;
            } else {
                //header($header['name'] . ': ' . $header['value'], $header['replace']);
            }
        }

        if (!$httpCodeSent) {
            //header('HTTP/1.1 ' . $this->_httpResponseCode);
            $httpCodeSent = true;
        }

        // End code from Zend_Controller_Response_Abstract --------------------------

        // Addition for test response object

        $this->setHeadersSentFlag(true);

        // End test response object addition

        return $this;
    }

    /**
     * Do everything except output any content.
     */
    public function sendResponse()
    {
        ob_start();
        $result = parent::sendResponse();
        ob_end_clean();
        return $result;
    }
}