diff --git a/tests/Bootstrap.php b/tests/Bootstrap.php
index 1c666d5..ea8d8ae 100644
--- a/tests/Bootstrap.php
+++ b/tests/Bootstrap.php
@@ -8,10 +8,7 @@
 
 // Path constants
 defined('PROJECT_BASE') OR define('PROJECT_BASE', realpath($dir.'/../').'/');
-defined('BASEPATH') OR define('BASEPATH', PROJECT_BASE.'system/');
-defined('APPPATH') OR define('APPPATH', PROJECT_BASE.'application/');
-defined('VIEWPATH') OR define('VIEWPATH', PROJECT_BASE.'');
-isset($_SERVER['REMOTE_ADDR']) OR $_SERVER['REMOTE_ADDR'] = '127.0.0.1';
+defined('SYSTEM_PATH') OR define('SYSTEM_PATH', PROJECT_BASE.'system/');
 
 // Get vfsStream either via PEAR or composer
 foreach (explode(PATH_SEPARATOR, get_include_path()) as $path)
@@ -31,8 +28,17 @@
 	class_alias('org\bovigo\vfs\vfsStreamWrapper', 'vfsStreamWrapper');
 }
 
+// Define CI path constants to VFS (filesystem setup in CI_TestCase::setUp)
+defined('BASEPATH') OR define('BASEPATH', vfsStream::url('system/'));
+defined('APPPATH') OR define('APPPATH', vfsStream::url('application/'));
+defined('VIEWPATH') OR define('VIEWPATH', APPPATH.'views/');
+
+// Set localhost "remote" IP
+isset($_SERVER['REMOTE_ADDR']) OR $_SERVER['REMOTE_ADDR'] = '127.0.0.1';
+
 // Prep our test environment
 include_once $dir.'/mocks/core/common.php';
+include_once SYSTEM_PATH.'core/common.php';
 include_once $dir.'/mocks/autoloader.php';
 spl_autoload_register('autoload');
 
diff --git a/tests/codeigniter/core/Lang_test.php b/tests/codeigniter/core/Lang_test.php
index a410dab..3364362 100644
--- a/tests/codeigniter/core/Lang_test.php
+++ b/tests/codeigniter/core/Lang_test.php
@@ -17,6 +17,7 @@
 
 	public function test_load()
 	{
+		$this->ci_vfs_clone('system/language/english/profiler_lang.php');
 		$this->assertTrue($this->lang->load('profiler', 'english'));
 		$this->assertEquals('URI STRING', $this->lang->line('profiler_uri_string'));
 	}
@@ -25,6 +26,7 @@
 
 	public function test_load_with_unspecified_language()
 	{
+		$this->ci_vfs_clone('system/language/english/profiler_lang.php');
 		$this->assertTrue($this->lang->load('profiler'));
 		$this->assertEquals('URI STRING', $this->lang->line('profiler_uri_string'));
 	}
diff --git a/tests/codeigniter/core/Loader_test.php b/tests/codeigniter/core/Loader_test.php
index db79e6a..69b2afb 100644
--- a/tests/codeigniter/core/Loader_test.php
+++ b/tests/codeigniter/core/Loader_test.php
@@ -9,11 +9,11 @@
 		// Instantiate a new loader
 		$this->load = new Mock_Core_Loader();
 
-		// mock up a ci instance
-		$this->ci_obj = new stdClass;
+		// Get CI instance
+		$this->ci_obj = $this->ci_instance();
 
-		// Fix get_instance()
-		$this->ci_instance($this->ci_obj);
+		// Set subclass prefix
+		$this->ci_set_config('subclass_prefix', 'MY_');
 	}
 
 	// --------------------------------------------------------------------
@@ -23,13 +23,10 @@
 	 */
 	public function test_library()
 	{
-		$this->_setup_config_mock();
-
 		// Create libraries directory with test library
 		$lib = 'unit_test_lib';
 		$class = 'CI_'.ucfirst($lib);
-		$content = '<?php class '.$class.' { } ';
-		$this->_create_content('libraries', $lib, $content, NULL, TRUE);
+		$this->ci_vfs_create($lib, '<?php class '.$class.' { }', $this->ci_base_root, 'libraries');
 
 		// Test loading as an array.
 		$this->assertNull($this->load->library(array($lib)));
@@ -50,13 +47,11 @@
 	 */
 	public function test_library_config()
 	{
-		$this->_setup_config_mock();
-
 		// Create libraries directory with test library
 		$lib = 'unit_test_config_lib';
 		$class = 'CI_'.ucfirst($lib);
-		$content = '<?php class '.$class.' { public function __construct($params) { $this->config = $params; } } ';
-		$this->_create_content('libraries', $lib, $content, NULL, TRUE);
+		$content = '<?php class '.$class.' { public function __construct($params) { $this->config = $params; } }';
+		$this->ci_vfs_create($lib, $content, $this->ci_base_root, 'libraries');
 
 		// Create config file
 		$cfg = array(
@@ -64,7 +59,7 @@
 			'bar' => 'baz',
 			'baz' => false
 		);
-		$this->_create_content('config', $lib, '<?php $config = '.var_export($cfg, TRUE).';');
+		$this->ci_vfs_create($lib, '<?php $config = '.var_export($cfg, TRUE).';', $this->ci_app_root, 'config');
 
 		// Test object name and config
 		$obj = 'testy';
@@ -81,13 +76,10 @@
 	 */
 	public function test_load_library_in_application_dir()
 	{
-		$this->_setup_config_mock();
-
 		// Create libraries directory in app path with test library
 		$lib = 'super_test_library';
 		$class = ucfirst($lib);
-		$content = '<?php class '.$class.' {} ';
-		$this->_create_content('libraries', $lib, $content);
+		$this->ci_vfs_create($lib, '<?php class '.$class.' { }', $this->ci_app_root, 'libraries');
 
 		// Load library
 		$this->assertNull($this->load->library($lib));
@@ -104,14 +96,12 @@
 	 */
 	public function test_driver()
 	{
-		$this->_setup_config_mock();
-
 		// Create libraries directory with test driver
 		$driver = 'unit_test_driver';
 		$dir = ucfirst($driver);
 		$class = 'CI_'.$dir;
 		$content = '<?php class '.$class.' { } ';
-		$this->_create_content('libraries', $driver, $content, $dir, TRUE);
+		$this->ci_vfs_create($driver, $content, $this->ci_base_root, 'libraries/'.$dir);
 
 		// Test loading as an array.
 		$this->assertNull($this->load->driver(array($driver)));
@@ -158,7 +148,7 @@
 		$model = 'unit_test_model';
 		$class = ucfirst($model);
 		$content = '<?php class '.$class.' extends CI_Model {} ';
-		$this->_create_content('models', $model, $content);
+		$this->ci_vfs_create($model, $content, $this->ci_app_root, 'models');
 
 		// Load model
 		$this->assertNull($this->load->model($model));
@@ -190,7 +180,7 @@
 		// Create views directory with test view
 		$view = 'unit_test_view';
 		$content = 'This is my test page.  <?php echo $hello; ?>';
-		$this->_create_content('views', $view, $content);
+		$this->ci_vfs_create($view, $content, $this->ci_app_root, 'views');
 
 		// Use the optional return parameter in this test, so the view is not
 		// run through the output class.
@@ -224,10 +214,10 @@
 		$dir = 'views';
 		$file = 'ci_test_mock_file';
 		$content = 'Here is a test file, which we will load now.';
-		$this->_create_content($dir, $file, $content);
+		$this->ci_vfs_create($file, $content, $this->ci_app_root, $dir);
 
 		// Just like load->view(), take the output class out of the mix here.
-		$out = $this->load->file($this->load->app_path.$dir.'/'.$file.'.php', TRUE);
+		$out = $this->load->file(APPPATH.$dir.'/'.$file.'.php', TRUE);
 		$this->assertEquals($content, $out);
 
 		// Test non-existent file
@@ -261,7 +251,7 @@
 		$helper = 'test';
 		$func = '_my_helper_test_func';
 		$content = '<?php function '.$func.'() { return true; } ';
-		$this->_create_content('helpers', $helper.'_helper', $content);
+		$this->ci_vfs_create($helper.'_helper', $content, $this->ci_app_root, 'helpers');
 
 		// Load helper
 		$this->assertEquals(NULL, $this->load->helper($helper));
@@ -294,7 +284,7 @@
 			$funcs[] = $func;
 			$files[$helper.'_helper'] = '<?php function '.$func.'() { return true; } ';
 		}
-		$this->_create_content('helpers', $files, NULL, NULL, TRUE);
+		$this->ci_vfs_create($files, NULL, $this->ci_base_root, 'helpers');
 
 		// Load helpers
 		$this->assertEquals(NULL, $this->load->helpers($helpers));
@@ -321,14 +311,12 @@
 	 */
 	public function test_packages()
 	{
-		$this->_setup_config_mock();
-
 		// Create third-party directory in app path with model
 		$dir = 'third-party';
 		$lib = 'unit_test_package';
 		$class = 'CI_'.ucfirst($lib);
 		$content = '<?php class '.$class.' { } ';
-		$this->_create_content($dir, $lib, $content);
+		$this->ci_vfs_create($lib, $content, $this->ci_app_root, $dir);
 
 		// Test failed load without path
 		$this->setExpectedException(
@@ -342,7 +330,7 @@
 		$paths = $this->load->get_package_paths(TRUE);
 
 		// Add path and verify
-		$path = $this->load->app_path.$dir;
+		$path = APPPATH.$dir;
 		$this->assertNull($this->load->add_package_path($path));
 		$this->assertContains($path, $this->load->get_package_paths(TRUE));
 
@@ -362,7 +350,6 @@
 	 */
 	public function test_load_config()
 	{
-		$this->_setup_config_mock();
 		$this->assertNull($this->load->config('config', FALSE));
 	}
 
@@ -373,35 +360,29 @@
 	 */
 	public function test_autoloader()
 	{
-		$this->_setup_config_mock();
-
 		// Create helper directory in app path with test helper
 		$helper = 'autohelp';
 		$hlp_func = '_autohelp_test_func';
-		$this->_create_content('helpers', $helper.'_helper', '<?php function '.$hlp_func.'() { return true; } ');
+		$content = '<?php function '.$hlp_func.'() { return true; } ';
+		$this->ci_vfs_create($helper.'_helper', $content, $this->ci_app_root, 'helpers');
 
 		// Create libraries directory in base path with test library
 		$lib = 'autolib';
 		$lib_class = 'CI_'.ucfirst($lib);
-		$this->_create_content('libraries', $lib, '<?php class '.$lib_class.' { } ', NULL, TRUE);
+		$this->ci_vfs_create($lib, '<?php class '.$lib_class.' { }', $this->ci_base_root, 'libraries');
 
-		// Create libraries subdirectory with test driver
-		// Since libraries/ now exists, we have to look it up and
-	   	// add the subdir directly instead of using _create_content
+		// Create test driver
 		$drv = 'autodrv';
 		$subdir = ucfirst($drv);
 		$drv_class = 'CI_'.$subdir;
-		$tree = array(
-			$subdir => array($drv.'.php' => '<?php class '.$drv_class.' { } ')
-		);
-		vfsStream::create($tree, $this->load->base_root->getChild('libraries'));
+		$this->ci_vfs_create($drv, '<?php class '.$drv_class.' { }', $this->ci_base_root, 'libraries/'.$subdir);
 
 		// Create package directory in app path with model
 		$dir = 'testdir';
-		$path = $this->load->app_path.$dir.'/';
+		$path = APPPATH.$dir.'/';
 		$model = 'automod';
 		$mod_class = ucfirst($model);
-		$this->_create_content($dir, $model, '<?php class '.$mod_class.' { } ', 'models');
+		$this->ci_vfs_create($model, '<?php class '.$mod_class.' { }', $this->ci_app_root, $dir.'/models');
 
 		// Create autoloader config
 		$cfg = array(
@@ -412,7 +393,7 @@
 			'model' => array($model),
 			'config' => array()
 		);
-		$this->_create_content('config', 'autoload', '<?php $autoload = '.var_export($cfg, TRUE).';');
+		$this->ci_vfs_create('autoload', '<?php $autoload = '.var_export($cfg, TRUE).';', $this->ci_app_root, 'config');
 
 		// Run autoloader
 		$this->load->autoload();
@@ -436,55 +417,4 @@
 		$this->assertAttributeInstanceOf($mod_class, $model, $this->ci_obj);
 	}
 
-	// --------------------------------------------------------------------
-
-	private function _setup_config_mock()
-	{
-		// Mock up a config object so config() has something to call
-		$config = $this->getMock('CI_Config', array('load'), array(), '', FALSE);
-		$config->expects($this->any())
-			   ->method('load')
-			   ->will($this->returnValue(TRUE));
-
-		// Reinitialize config paths to use VFS
-		$config->_config_paths = array($this->load->app_path);
-
-		// Add the mock to our stdClass
-		$this->ci_instance_var('config', $config);
-	}
-
-	// --------------------------------------------------------------------
-
-	private function _create_content($dir, $file, $content, $sub = NULL, $base = FALSE)
-	{
-		// Create structure containing directory
-		$tree = array($dir => array());
-
-		// Check for subdirectory
-		if ($sub) {
-			// Add subdirectory to tree and get reference
-			$tree[$dir][$sub] = array();
-			$leaf =& $tree[$dir][$sub];
-		}
-		else {
-			// Get reference to main directory
-			$leaf =& $tree[$dir];
-		}
-
-		// Check for multiple files
-		if (is_array($file)) {
-			// Add multiple files to directory
-			foreach ($file as $name => $data) {
-				$leaf[$name.'.php'] = $data;
-			}
-		}
-		else {
-			// Add single file with content
-			$leaf[$file.'.php'] = $content;
-		}
-
-		// Create structure under app or base path
-		vfsStream::create($tree, $base ? $this->load->base_root : $this->load->app_root);
-	}
-
-}
+}
\ No newline at end of file
diff --git a/tests/codeigniter/helpers/date_helper_test.php b/tests/codeigniter/helpers/date_helper_test.php
index 9feade7..1458acd 100644
--- a/tests/codeigniter/helpers/date_helper_test.php
+++ b/tests/codeigniter/helpers/date_helper_test.php
@@ -168,6 +168,8 @@
 
 	public function test_timespan()
 	{
+		$this->ci_vfs_clone('system/language/english/date_lang.php');
+
 		$loader_cls = $this->ci_core_class('load');
 		$this->ci_instance_var('load', new $loader_cls);
 
diff --git a/tests/codeigniter/helpers/form_helper_test.php b/tests/codeigniter/helpers/form_helper_test.php
index 1a30ed9..48628d2 100644
--- a/tests/codeigniter/helpers/form_helper_test.php
+++ b/tests/codeigniter/helpers/form_helper_test.php
@@ -1,10 +1,12 @@
 <?php
 
-require BASEPATH . 'core/Common.php';
-require BASEPATH . 'helpers/form_helper.php';
-
 class Form_helper_test extends CI_TestCase
 {
+	public function set_up()
+	{
+		$this->helper('form');
+	}
+
 	public function test_form_hidden()
 	{
 		$expected = <<<EOH
diff --git a/tests/codeigniter/helpers/number_helper_test.php b/tests/codeigniter/helpers/number_helper_test.php
index ef6aae1..817db2c 100644
--- a/tests/codeigniter/helpers/number_helper_test.php
+++ b/tests/codeigniter/helpers/number_helper_test.php
@@ -11,31 +11,18 @@
 
 		// Mock away load, too much going on in there,
 		// we'll just check for the expected parameter
-
 		$lang = $this->getMock($lang_cls, array('load'));
 		$lang->expects($this->once())
 			 ->method('load')
 			 ->with($this->equalTo('number'));
 
 		// Assign the proper language array
-
-		$lang->language = $this->_get_lang('number');
+		$lang->language = $this->lang('number');
 
 		// We don't have a controller, so just create
 		// a cheap class to act as our super object.
 		// Make sure it has a lang attribute.
-
-		$obj = new stdClass;
-		$obj->lang = $lang;
-		$this->ci_instance($obj);
-	}
-
-	// Quick helper to actually grab the language
-	// file. Consider moving this to ci_testcase?
-	public function _get_lang($name)
-	{
-		require BASEPATH.'language/english/'.$name.'_lang.php';
-		return $lang;
+		$this->ci_instance_var('lang', $lang);
 	}
 
 	public function test_byte_format()
diff --git a/tests/codeigniter/helpers/text_helper_test.php b/tests/codeigniter/helpers/text_helper_test.php
index f131469..d75d262 100644
--- a/tests/codeigniter/helpers/text_helper_test.php
+++ b/tests/codeigniter/helpers/text_helper_test.php
@@ -64,6 +64,7 @@
 
 	public function test_convert_accented_characters()
 	{
+		$this->ci_vfs_clone('application/config/foreign_chars.php');
 		$this->assertEquals('AAAeEEEIIOOEUUUeY', convert_accented_characters('ÀÂÄÈÊËÎÏÔŒÙÛÜŸ'));
 		$this->assertEquals('a e i o u n ue', convert_accented_characters('á é í ó ú ñ ü'));
 	}
diff --git a/tests/codeigniter/libraries/Encrypt_test.php b/tests/codeigniter/libraries/Encrypt_test.php
index 153a25e..998d806 100644
--- a/tests/codeigniter/libraries/Encrypt_test.php
+++ b/tests/codeigniter/libraries/Encrypt_test.php
@@ -4,11 +4,8 @@
 
 	public function set_up()
 	{
-		$obj = new stdClass;
-		$obj->encrypt = new Mock_Libraries_Encrypt();
-
-		$this->ci_instance($obj);
-		$this->encrypt = $obj->encrypt;
+		$this->encrypt = new Mock_Libraries_Encrypt();
+		$this->ci_instance_var('encrypt', $this->encrypt);
 
 		$this->ci_set_config('encryption_key', "Encryptin'glike@boss!");
 		$this->msg = 'My secret message';
diff --git a/tests/codeigniter/libraries/Parser_test.php b/tests/codeigniter/libraries/Parser_test.php
index b68f44a..394c226 100644
--- a/tests/codeigniter/libraries/Parser_test.php
+++ b/tests/codeigniter/libraries/Parser_test.php
@@ -4,12 +4,8 @@
 
 	public function set_up()
 	{
-		$obj = new stdClass;
-		$obj->parser = new Mock_Libraries_Parser();
-
-		$this->ci_instance($obj);
-
-		$this->parser = $obj->parser;
+		$this->parser = new Mock_Libraries_Parser();
+		$this->ci_instance_var('parser', $this->parser);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/tests/codeigniter/libraries/Session_test.php b/tests/codeigniter/libraries/Session_test.php
index 60d3a5b..14469f7 100644
--- a/tests/codeigniter/libraries/Session_test.php
+++ b/tests/codeigniter/libraries/Session_test.php
@@ -29,13 +29,15 @@
 		$_COOKIE = array();
 
 		// Establish necessary support classes
-		$obj = new stdClass;
 		$cfg = $this->ci_core_class('cfg');
-		$obj->config = new $cfg();
 		$ldr = $this->ci_core_class('load');
-		$obj->load = new $ldr();
-		$obj->input = new Mock_Core_Input(NULL, NULL);
-		$this->ci_instance($obj);
+		$ci = $this->ci_instance();
+		$ci->config = new $cfg();
+		$ci->load = new $ldr();
+		$ci->input = new Mock_Core_Input(NULL, NULL);
+
+		// Make sure string helper is available
+		$this->ci_vfs_clone('system/helpers/string_helper.php');
 
 		// Attach session instance locally
 		$config = array(
diff --git a/tests/codeigniter/libraries/Table_test.php b/tests/codeigniter/libraries/Table_test.php
index edfc83d..ce04b6a 100644
--- a/tests/codeigniter/libraries/Table_test.php
+++ b/tests/codeigniter/libraries/Table_test.php
@@ -4,12 +4,8 @@
 
 	public function set_up()
 	{
-		$obj = new stdClass;
-		$obj->table = new Mock_Libraries_Table();
-
-		$this->ci_instance($obj);
-
-		$this->table = $obj->table;
+		$this->table = new Mock_Libraries_Table();
+		$this->ci_instance_var('table', $this->table);
 	}
 
 	// Setter Methods
diff --git a/tests/codeigniter/libraries/Typography_test.php b/tests/codeigniter/libraries/Typography_test.php
index eb6dacb..5dba062 100644
--- a/tests/codeigniter/libraries/Typography_test.php
+++ b/tests/codeigniter/libraries/Typography_test.php
@@ -4,12 +4,8 @@
 
 	public function set_up()
 	{
-		$obj = new stdClass;
-		$obj->type = new Mock_Libraries_Typography();
-
-		$this->ci_instance($obj);
-
-		$this->type = $obj->type;
+		$this->type = new Mock_Libraries_Typography();
+		$this->ci_instance('type', $this->type);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/tests/codeigniter/libraries/Upload_test.php b/tests/codeigniter/libraries/Upload_test.php
index d79a3ff..8279427 100644
--- a/tests/codeigniter/libraries/Upload_test.php
+++ b/tests/codeigniter/libraries/Upload_test.php
@@ -4,18 +4,11 @@
 
 	function set_up()
 	{
-		$obj = new stdClass;
-		$obj->upload = new Mock_Libraries_Upload();
-		$obj->security = new Mock_Core_Security();
-		$obj->lang = new Mock_Core_Lang();
-
-		$this->ci_instance($obj);
-		$this->upload = $obj->upload;
-
-		vfsStreamWrapper::register();
-		vfsStreamWrapper::setRoot(new vfsStreamDirectory('testDir'));
-
-		$this->_test_dir = vfsStreamWrapper::getRoot();
+		$ci = $this->ci_instance();
+		$ci->upload = new Mock_Libraries_Upload();
+		$ci->security = new Mock_Core_Security();
+		$ci->lang = new Mock_Core_Lang();
+		$this->upload = $ci->upload;
 	}
 
 	function test_do_upload() 
@@ -64,11 +57,15 @@
 
 	function test_set_filename()
 	{
-		$file1 = vfsStream::newFile('hello-world.txt')->withContent('Hello world.')->at($this->_test_dir);
+		$dir = 'uploads';
+		$isnew = 'helloworld.txt';
+		$exists = 'hello-world.txt';
+		$this->ci_vfs_create($exists, 'Hello world.', $this->ci_app_root, $dir);
+		$path = $this->ci_vfs_path($dir.'/', APPPATH);
 		$this->upload->file_ext = '.txt';
 
-		$this->assertEquals('helloworld.txt', $this->upload->set_filename(vfsStream::url('testDir').'/', 'helloworld.txt'));
-		$this->assertEquals('hello-world1.txt', $this->upload->set_filename(vfsStream::url('testDir').'/', 'hello-world.txt'));
+		$this->assertEquals($isnew, $this->upload->set_filename($path, $isnew));
+		$this->assertEquals('hello-world1.txt', $this->upload->set_filename($path, $exists));
 	}
 
 	function test_set_max_filesize()
@@ -107,7 +104,7 @@
 	function test_set_image_properties()
 	{
 		$this->upload->file_type = 'image/gif';
-		$this->upload->file_temp = 'tests/mocks/uploads/ci_logo.gif';
+		$this->upload->file_temp = realpath(PROJECT_BASE.'tests/mocks/uploads/ci_logo.gif');
 
 		$props = array(
 			'image_width'	=>	170,
@@ -156,7 +153,7 @@
 		$this->assertTrue($this->upload->is_allowed_filetype(FALSE));
 		$this->assertTrue($this->upload->is_allowed_filetype(TRUE));
 
-		$this->upload->file_temp = 'tests/mocks/uploads/ci_logo.gif';
+		$this->upload->file_temp = realpath(PROJECT_BASE.'tests/mocks/uploads/ci_logo.gif');
 		$this->upload->file_ext = '.gif';
 		$this->upload->file_type = 'image/gif';
 		$this->assertTrue($this->upload->is_allowed_filetype());
@@ -179,7 +176,7 @@
 		$this->assertTrue($this->upload->is_allowed_dimensions());
 
 		$this->upload->file_type = 'image/gif';
-		$this->upload->file_temp = 'tests/mocks/uploads/ci_logo.gif';
+		$this->upload->file_temp = realpath(PROJECT_BASE.'tests/mocks/uploads/ci_logo.gif');
 
 		$this->upload->max_width = 10;		
 		$this->assertFalse($this->upload->is_allowed_dimensions());
@@ -197,7 +194,9 @@
 		$this->upload->upload_path = '';
 		$this->assertFalse($this->upload->validate_upload_path());
 
-		$this->upload->upload_path = vfsStream::url('testDir');
+		$dir = 'uploads';
+		$this->ci_vfs_mkdir($dir);
+		$this->upload->upload_path = $this->ci_vfs_path($dir);
 		$this->assertTrue($this->upload->validate_upload_path());
 	}
 
@@ -222,20 +221,24 @@
 
 	function test_do_xss_clean()
 	{
-		$file1 = vfsStream::newFile('file1.txt')->withContent('The billy goat was waiting for them.')->at($this->_test_dir);
-		$file2 = vfsStream::newFile('file2.txt')->at($this->_test_dir);
-		$file3 = vfsStream::newFile('file3.txt')->withContent('<script type="text/javascript">alert("Boo! said the billy goat")</script>')->at($this->_test_dir);
+		$dir = 'uploads';
+		$file1 = 'file1.txt';
+		$file2 = 'file2.txt';
+		$file3 = 'file3.txt';
+		$this->ci_vfs_create($file1, 'The billy goat was waiting for them.', $this->ci_vfs_root, $dir);
+		$this->ci_vfs_create($file2, '', $this->ci_vfs_root, $dir);
+		$this->ci_vfs_create($file3, '<script type="text/javascript">alert("Boo! said the billy goat")</script>', $this->ci_vfs_root, $dir);
 
-		$this->upload->file_temp = vfsStream::url('file1.txt');
+		$this->upload->file_temp = $this->ci_vfs_path($file1, $dir);
 		$this->assertTrue($this->upload->do_xss_clean());
 
-		$this->upload->file_temp = vfsStream::url('file2.txt');
+		$this->upload->file_temp = $this->ci_vfs_path($file2, $dir);
 		$this->assertFalse($this->upload->do_xss_clean());
 
-		$this->upload->file_temp = vfsStream::url('file3.txt');
+		$this->upload->file_temp = $this->ci_vfs_path($file3, $dir);
 		$this->assertFalse($this->upload->do_xss_clean());
 
-		$this->upload->file_temp = 'tests/mocks/uploads/ci_logo.gif';
+		$this->upload->file_temp = realpath(PROJECT_BASE.'tests/mocks/uploads/ci_logo.gif');
 		$this->assertTrue($this->upload->do_xss_clean());
 	}
 
diff --git a/tests/codeigniter/libraries/Useragent_test.php b/tests/codeigniter/libraries/Useragent_test.php
index 89383f8..e372655 100644
--- a/tests/codeigniter/libraries/Useragent_test.php
+++ b/tests/codeigniter/libraries/Useragent_test.php
@@ -10,12 +10,11 @@
 		// set a baseline user agent
 		$_SERVER['HTTP_USER_AGENT'] = $this->_user_agent;
 
-		$obj = new stdClass;
-		$obj->agent = new Mock_Libraries_UserAgent();
+		$this->ci_vfs_clone('application/config/user_agents.php');
 
-		$this->ci_instance($obj);
+		$this->agent = new Mock_Libraries_UserAgent();
 
-		$this->agent = $obj->agent;
+		$this->ci_instance_var('agent', $this->agent);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/tests/mocks/autoloader.php b/tests/mocks/autoloader.php
index 88d016b..431c310 100644
--- a/tests/mocks/autoloader.php
+++ b/tests/mocks/autoloader.php
@@ -48,32 +48,32 @@
 
 		if (in_array($subclass, $ci_core))
 		{
-			$dir = BASEPATH.'core'.DIRECTORY_SEPARATOR;
+			$dir = SYSTEM_PATH.'core'.DIRECTORY_SEPARATOR;
 			$class = $subclass;
 		}
 		elseif (in_array($subclass, $ci_libraries))
 		{
-			$dir = BASEPATH.'libraries'.DIRECTORY_SEPARATOR;
+			$dir = SYSTEM_PATH.'libraries'.DIRECTORY_SEPARATOR;
 			$class = ($subclass === 'Driver_Library') ? 'Driver' : $subclass;
 		}
 		elseif (in_array($subclass, $ci_drivers))
 		{
-			$dir = BASEPATH.'libraries'.DIRECTORY_SEPARATOR.$subclass.DIRECTORY_SEPARATOR;
+			$dir = SYSTEM_PATH.'libraries'.DIRECTORY_SEPARATOR.$subclass.DIRECTORY_SEPARATOR;
 			$class = $subclass;
 		}
 		elseif (in_array(($parent = strtok($subclass, '_')), $ci_drivers)) {
-			$dir = BASEPATH.'libraries'.DIRECTORY_SEPARATOR.$parent.DIRECTORY_SEPARATOR.'drivers'.DIRECTORY_SEPARATOR;
+			$dir = SYSTEM_PATH.'libraries'.DIRECTORY_SEPARATOR.$parent.DIRECTORY_SEPARATOR.'drivers'.DIRECTORY_SEPARATOR;
 			$class = $subclass;
 		}
 		elseif (preg_match('/^CI_DB_(.+)_(driver|forge|result|utility)$/', $class, $m) && count($m) === 3)
 		{
-			$driver_path = BASEPATH.'database'.DIRECTORY_SEPARATOR.'drivers'.DIRECTORY_SEPARATOR;
+			$driver_path = SYSTEM_PATH.'database'.DIRECTORY_SEPARATOR.'drivers'.DIRECTORY_SEPARATOR;
 			$dir = $driver_path.$m[1].DIRECTORY_SEPARATOR;
 			$file = $dir.$m[1].'_'.$m[2].'.php';
 		}
 		elseif (strpos($class, 'CI_DB') === 0)
 		{
-			$dir = BASEPATH.'database'.DIRECTORY_SEPARATOR;
+			$dir = SYSTEM_PATH.'database'.DIRECTORY_SEPARATOR;
 			$file = $dir.str_replace(array('CI_DB','active_record'), array('DB', 'active_rec'), $subclass).'.php';
 		}
 		else
diff --git a/tests/mocks/ci_testcase.php b/tests/mocks/ci_testcase.php
index eda9e1b..980e912 100644
--- a/tests/mocks/ci_testcase.php
+++ b/tests/mocks/ci_testcase.php
@@ -2,7 +2,9 @@
 
 class CI_TestCase extends PHPUnit_Framework_TestCase {
 
-	protected $ci_config;
+	public $ci_vfs_root;
+	public $ci_app_root;
+	public $ci_base_root;
 	protected $ci_instance;
 	protected static $ci_test_instance;
 
@@ -25,13 +27,18 @@
 	public function __construct()
 	{
 		parent::__construct();
-		$this->ci_config = array();
+		$this->ci_instance = new StdClass();
 	}
 
 	// --------------------------------------------------------------------
 
 	public function setUp()
 	{
+		// Setup VFS with base directories
+		$this->ci_vfs_root = vfsStream::setup();
+		$this->ci_app_root = vfsStream::newDirectory('application')->at($this->ci_vfs_root);
+		$this->ci_base_root = vfsStream::newDirectory('system')->at($this->ci_vfs_root);
+
 		if (method_exists($this, 'set_up'))
 		{
 			$this->set_up();
@@ -57,15 +64,27 @@
 
 	// --------------------------------------------------------------------
 
-	public function ci_set_config($key, $val = '')
+	public function ci_set_config($key = '', $val = '')
 	{
+		// Add test config
+		if ( ! isset($this->ci_instance->config))
+		{
+			$this->ci_instance->config = new CI_TestConfig();
+		}
+
+		// Empty key means just do setup above
+		if ($key === '')
+		{
+			return;
+		}
+
 		if (is_array($key))
 		{
-			$this->ci_config = $key;
+			$this->ci_instance->config->config = $key;
 		}
 		else
 		{
-			$this->ci_config[$key] = $val;
+			$this->ci_instance->config->config[$key] = $val;
 		}
 	}
 
@@ -73,7 +92,7 @@
 
 	public function ci_get_config()
 	{
-		return $this->ci_config;
+		return isset($this->ci_instance->config) ? $this->ci_instance->config->config : array();
 	}
 
 	// --------------------------------------------------------------------
@@ -132,7 +151,7 @@
 
 		if ( ! class_exists('CI_'.$class_name))
 		{
-			require_once BASEPATH.'core/'.$class_name.'.php';
+			require_once SYSTEM_PATH.'core/'.$class_name.'.php';
 		}
 
 		$GLOBALS[strtoupper($global_name)] = 'CI_'.$class_name;
@@ -148,6 +167,155 @@
 		$orig = $obj;
 	}
 
+	/**
+	 * Create VFS directory
+	 *
+	 * @param	string	Directory name
+	 * @param	object	Optional root to create in
+	 * @return	object	New directory object
+	 */
+	public function ci_vfs_mkdir($name, $root = NULL)
+	{
+		// Check for root
+		if ( ! $root)
+		{
+			$root = $this->ci_vfs_root;
+		}
+
+		// Return new directory object
+		return vfsStream::newDirectory($name)->at($root);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Create VFS content
+	 *
+	 * @param	string	File name
+	 * @param	string	File content
+	 * @param	object	VFS directory object
+	 * @param	mixed	Optional subdirectory path or array of subs
+	 * @return	void
+	 */
+	public function ci_vfs_create($file, $content = '', $root = NULL, $path = NULL)
+	{
+		// Check for array
+		if (is_array($file))
+		{
+			foreach ($file as $name => $content)
+			{
+				$this->ci_vfs_create($name, $content, $root, $path);
+			}
+			return;
+		}
+
+		// Assert .php extension if none given
+		if (pathinfo($file, PATHINFO_EXTENSION) == '')
+		{
+			$file .= '.php';
+		}
+
+		// Build content
+		$tree = array($file => $content);
+
+		// Check for path
+		$subs = array();
+		if ($path)
+		{
+			// Explode if not array
+			$subs = is_array($path) ? $path : explode('/', trim($path, '/'));
+		}
+
+		// Check for root
+		if ( ! $root)
+		{
+			// Use base VFS root
+			$root = $this->ci_vfs_root;
+		}
+
+		// Handle subdirectories
+		while (($dir = array_shift($subs)))
+		{
+			// See if subdir exists under current root
+			$dir_root = $root->getChild($dir);
+			if ($dir_root)
+			{
+			   	// Yes - recurse into subdir
+				$root = $dir_root;
+			}
+			else
+			{
+				// No - put subdirectory back and quit
+				array_unshift($subs, $dir);
+				break;
+			}
+		}
+
+		// Create any remaining subdirectories
+		if ($subs)
+		{
+			foreach (array_reverse($subs) as $dir)
+			{
+				// Wrap content in subdirectory for creation
+				$tree = array($dir => $tree);
+			}
+		}
+
+		// Create tree
+		vfsStream::create($tree, $root);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Clone a real file into VFS
+	 *
+	 * @param	string	Path from base directory
+	 * @return	bool	TRUE on success, otherwise FALSE
+	 */
+	public function ci_vfs_clone($path)
+	{
+		// Get real file contents
+		$content = file_get_contents(PROJECT_BASE.$path);
+		if ($content === FALSE)
+		{
+			// Couldn't find file to clone
+			return FALSE;
+		}
+
+		$this->ci_vfs_create(basename($path), $content, NULL, dirname($path));
+		return TRUE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Helper to get a VFS URL path
+	 *
+	 * @param	string	Path
+	 * @param	string	Optional base path
+	 * @return	string	Path URL
+	 */
+	public function ci_vfs_path($path, $base = '')
+	{
+		// Check for base path
+		if ($base)
+		{
+			// Prepend to path
+			$path = rtrim($base, '/').'/'.ltrim($path, '/');
+
+			// Is it already in URL form?
+			if (strpos($path, '://') !== FALSE)
+			{
+				// Done - return path
+				return $path;
+			}
+		}
+
+		// Trim leading slash and return URL
+		return vfsStream::url(ltrim($path, '/'));
+	}
+
 	// --------------------------------------------------------------------
 	// Internals
 	// --------------------------------------------------------------------
@@ -171,7 +339,15 @@
 
 	public function helper($name)
 	{
-		require_once(BASEPATH.'helpers/'.$name.'_helper.php');
+		require_once(SYSTEM_PATH.'helpers/'.$name.'_helper.php');
+	}
+
+	// --------------------------------------------------------------------
+
+	public function lang($name)
+	{
+		require(SYSTEM_PATH.'language/english/'.$name.'_lang.php');
+		return $lang;
 	}
 
 	// --------------------------------------------------------------------
diff --git a/tests/mocks/ci_testconfig.php b/tests/mocks/ci_testconfig.php
new file mode 100644
index 0000000..eb318dd
--- /dev/null
+++ b/tests/mocks/ci_testconfig.php
@@ -0,0 +1,18 @@
+<?php
+
+class CI_TestConfig {
+
+	public $config = array();
+	public $_config_paths = array(APPPATH);
+
+	public function item($key)
+	{
+		return isset($this->config[$key]) ? $this->config[$key] : FALSE;
+	}
+
+	public function load($arg1, $arg2, $arg3)
+	{
+		return TRUE;
+	}
+
+}
diff --git a/tests/mocks/core/common.php b/tests/mocks/core/common.php
index a655ee1..b001074 100644
--- a/tests/mocks/core/common.php
+++ b/tests/mocks/core/common.php
@@ -39,6 +39,30 @@
 	}
 }
 
+if ( ! function_exists('get_mimes'))
+{
+	/**
+	 * Returns the MIME types array from config/mimes.php
+	 *
+	 * @return	array
+	 */
+	function &get_mimes()
+	{
+		static $_mimes = array();
+
+		if (empty($_mimes))
+		{
+			$path = realpath(PROJECT_BASE.'application/config/mimes.php');
+			if (is_file($path))
+			{
+				$_mimes = include($path);
+			}
+		}
+
+		return $_mimes;
+	}
+}
+
 // --------------------------------------------------------------------
 
 if ( ! function_exists('load_class'))
@@ -166,4 +190,4 @@
 	{
 		return TRUE;
 	}
-}
\ No newline at end of file
+}
diff --git a/tests/mocks/core/loader.php b/tests/mocks/core/loader.php
index 9eb7825..7ea4da3 100644
--- a/tests/mocks/core/loader.php
+++ b/tests/mocks/core/loader.php
@@ -3,36 +3,6 @@
 class Mock_Core_Loader extends CI_Loader {
 
 	/**
-	 * Since we use paths to load up models, views, etc, we need the ability to
-	 * mock up the file system so when core tests are run, we aren't mucking
-	 * in the application directory. This will give finer grained control over
-	 * these tests. Also, by mocking the system directory, we eliminate dependency
-	 * on any other classes so errors in libraries, helpers, etc. don't give false
-	 * negatives for the actual loading process. So yeah, while this looks odd,
-	 * I need to overwrite protected class vars in the loader. So here we go...
-	 *
-	 * @covers CI_Loader::__construct()
-	 */
-	public function __construct()
-	{
-		// Create VFS tree of loader locations
-		$this->root = vfsStream::setup();
-		$this->app_root = vfsStream::newDirectory('application')->at($this->root);
-		$this->base_root = vfsStream::newDirectory('system')->at($this->root);
-
-		// Get VFS app and base path URLs
-		$this->app_path = vfsStream::url('application').'/';
-		$this->base_path = vfsStream::url('system').'/';
-
-		// Set loader paths with VFS URLs
-		$this->_ci_ob_level  		= ob_get_level();
-		$this->_ci_library_paths	= array($this->app_path, $this->base_path);
-		$this->_ci_helper_paths 	= array($this->app_path, $this->base_path);
-		$this->_ci_model_paths 		= array($this->app_path);
-		$this->_ci_view_paths 		= array($this->app_path.'views/' => TRUE);
-	}
-
-	/**
 	 * Give public access to _ci_autoloader for testing
 	 */
 	public function autoload()