diff --git a/index.php b/index.php
index ab34dc6830..9906979fe0 100644
--- a/index.php
+++ b/index.php
@@ -188,6 +188,46 @@ $loader->initialize(new Config\Autoload());
 // the psr4 loader.
 $loader->register();
 
+/*
+ * ------------------------------------------------------
+ *  Load the global functions
+ * ------------------------------------------------------
+ */
+
+require_once BASEPATH.'Common.php';
+
+/*
+ * ------------------------------------------------------
+ *  Set custom exception handling
+ * ------------------------------------------------------
+ */
+$config = new \Config\App();
+
+Config\Services::exceptions($config, true)
+	->initialize();
+
+//--------------------------------------------------------------------
+// Should we use a Composer autoloader?
+//--------------------------------------------------------------------
+
+if ($composer_autoload = $config->composerAutoload)
+{
+	if ($composer_autoload === TRUE)
+	{
+		file_exists(APPPATH.'vendor/autoload.php')
+			? require_once(APPPATH.'vendor/autoload.php')
+			: log_message('error', '$config->\'composerAutoload\' is set to TRUE but '.APPPATH.'vendor/autoload.php was not found.');
+	}
+	elseif (file_exists($composer_autoload))
+	{
+		require_once($composer_autoload);
+	}
+	else
+	{
+		log_message('error', 'Could not find the specified $config->\'composerAutoload\' path: '.$composer_autoload);
+	}
+}
+
 /*
  * --------------------------------------------------------------------
  * LOAD THE BOOTSTRAP FILE
@@ -195,7 +235,5 @@ $loader->register();
  *
  * And away we go...
  */
-$config = new Config\App();
-new CodeIgniter\Bootstrap($config);
 $codeigniter = new CodeIgniter\CodeIgniter($startMemory, $startTime, $config);
 $codeigniter->run();
diff --git a/phpunit.xml b/phpunit.xml
index 032f2c5bbf..9423e325e6 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -18,7 +18,6 @@
         <whitelist processUncoveredFilesFromWhitelist="true">
             <directory suffix=".php">./system</directory>
             <exclude>
-                <file>./system/Bootstrap.php</file>
                 <file>./system/ComposerScripts.php</file>
                 <file>./system/View/Escaper.php</file>
                 <directory suffix=".php">./system/View/Exception</directory>
diff --git a/system/Bootstrap.php b/system/Bootstrap.php
deleted file mode 100644
index 26141399a4..0000000000
--- a/system/Bootstrap.php
+++ /dev/null
@@ -1,117 +0,0 @@
-<?php namespace CodeIgniter;
-
-/**
- * CodeIgniter
- *
- * An open source application development framework for PHP
- *
- * This content is released under the MIT License (MIT)
- *
- * Copyright (c) 2014 - 2016, British Columbia Institute of Technology
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- *
- * @package	CodeIgniter
- * @author	CodeIgniter Dev Team
- * @copyright	Copyright (c) 2014 - 2016, British Columbia Institute of Technology (http://bcit.ca/)
- * @license	http://opensource.org/licenses/MIT	MIT License
- * @link	http://codeigniter.com
- * @since	Version 4.0.0
- * @filesource
- */
-
-use Config\App;
-use Config\Services;
-use Config\Autoload;
-
-/**
- * Class Bootstrap
- *
- * @codeCoverageIgnore
- * @package CodeIgniter
- */
-class Bootstrap
-{
-	/**
-	 * The application configuration object.
-	 *
-	 * @var \Config\App
-	 */
-	protected $config;
-
-	//--------------------------------------------------------------------
-
-	public function __construct(App $config)
-	{
-		$this->config = $config;
-
-		require_once BASEPATH.'Common.php';
-
-		$this->setExceptionHandling();
-		$this->loadComposerAutoloader();
-	}
-	
-	//--------------------------------------------------------------------
-
-	/**
-	 * Set custom exception handling
-	 */
-	protected function setExceptionHandling()
-	{
-		Services::exceptions($this->config, true)
-			->initialize();
-	}
-
-	//--------------------------------------------------------------------
-
-	/**
-	 * Should we use a Composer autoloader?
-	 *
-	 * CodeIgniter provides its own PSR4-compatible autoloader, but many
-	 * third-party scripts will take advantage of the extra flexibility
-	 * that Composer provides. This allows that support to be provided,
-	 * and even with a customizable path to their autoloader.
-	 */
-	protected function loadComposerAutoloader()
-	{
-		$composer_autoload = $this->config->composerAutoload;
-
-		if (empty($composer_autoload))
-		{
-			return;
-		}
-
-		if ($composer_autoload === true)
-		{
-			file_exists(APPPATH.'vendor/autoload.php')
-				? require_once(APPPATH.'vendor/autoload.php')
-				: log_message('error', '$this->config->\'composerAutoload\' is set to TRUE but '.APPPATH.
-				'vendor/autoload.php was not found.');
-		}
-		elseif (file_exists($composer_autoload))
-		{
-			require_once($composer_autoload);
-		}
-		else
-		{
-			log_message('error',
-				'Could not find the specified $this->config->\'composerAutoload\' path: '.$composer_autoload);
-		}
-	}
-}
diff --git a/tests/_support/MockBootstrap.php b/tests/_support/MockBootstrap.php
deleted file mode 100644
index 91de5f1339..0000000000
--- a/tests/_support/MockBootstrap.php
+++ /dev/null
@@ -1,6 +0,0 @@
-<?php namespace CodeIgniter;
-
-class MockBootstrap extends Bootstrap
-{
-
-}
diff --git a/tests/_support/_bootstrap.php b/tests/_support/_bootstrap.php
index 7d8c60c172..6528e26d74 100644
--- a/tests/_support/_bootstrap.php
+++ b/tests/_support/_bootstrap.php
@@ -24,6 +24,7 @@ switch (ENVIRONMENT)
 }
 
 define('CI_DEBUG', 1);
+define('SHOW_DEBUG_BACKTRACE', TRUE);
 
 $system_path = '../../system';
 
@@ -31,69 +32,56 @@ $application_folder = '../../application';
 
 $writable_directory = '../../writable';
 
+// Ensure the current directory is pointing to the front controller's directory
+chdir(__DIR__);
 
-// Set the current directory correctly for CLI requests
-if (defined('STDIN'))
-{
-	chdir(__DIR__);
-}
-
-if (($_temp = realpath($system_path)) !== false)
-{
-	$system_path = $_temp.'/';
-}
-else
-{
-	// Ensure there's a trailing slash
-	$system_path = rtrim($system_path, '/').'/';
-}
-
-// Is the system path correct?
-if ( ! is_dir($system_path))
+// Are the system and application paths correct?
+if ( ! realpath($system_path) OR ! is_dir($system_path))
 {
 	header('HTTP/1.1 503 Service Unavailable.', true, 503);
 	echo 'Your system folder path does not appear to be set correctly. Please open the following file and correct this: '.
-	     pathinfo(__FILE__, PATHINFO_BASENAME);
+		pathinfo(__FILE__, PATHINFO_BASENAME);
 	exit(3); // EXIT_CONFIG
 }
 
+if ( ! realpath($application_folder) OR ! is_dir($application_folder))
+{
+	header('HTTP/1.1 503 Service Unavailable.', true, 503);
+	echo 'Your application folder path does not appear to be set correctly. Please open the following file and correct this: '.
+		pathinfo(__FILE__, PATHINFO_BASENAME);
+	exit(3); // EXIT_CONFIG
+}
+
+// The name of THIS file
+define('SELF', pathinfo(__FILE__, PATHINFO_BASENAME));
+
 // Path to the system folder
-define('BASEPATH', str_replace('\\', '/', $system_path));
+define('BASEPATH', realpath($system_path).DIRECTORY_SEPARATOR);
 
 // Path to the front controller (this file)
-define('FCPATH', realpath(__DIR__.'/../../') .'/');
-
-// The name of the INDEX file
-define('SELF', pathinfo(FCPATH.'index.php', PATHINFO_BASENAME));
+define('FCPATH', __DIR__.DIRECTORY_SEPARATOR);
 
 // Path to the writable directory.
-define('WRITEPATH', realpath(str_replace('\\', '/', $writable_directory)).'/');
+define('WRITEPATH', realpath($writable_directory).DIRECTORY_SEPARATOR);
 
 // The path to the "application" folder
-if (is_dir($application_folder))
-{
-	if (($_temp = realpath($application_folder)) !== false)
-	{
-		$application_folder = $_temp;
-	}
-
-	define('APPPATH', $application_folder.DIRECTORY_SEPARATOR);
-}
-else
-{
-	if ( ! is_dir(BASEPATH.$application_folder.DIRECTORY_SEPARATOR))
-	{
-		header('HTTP/1.1 503 Service Unavailable.', true, 503);
-		echo 'Your application folder path does not appear to be set correctly. Please open the following file and correct this: '.
-		     SELF;
-		exit(3); // EXIT_CONFIG
-	}
-
-	define('APPPATH', BASEPATH.$application_folder.DIRECTORY_SEPARATOR);
-}
+define('APPPATH', realpath($application_folder).DIRECTORY_SEPARATOR);
 
 define('SUPPORTPATH', realpath(BASEPATH.'../tests/_support/').'/');
 
+/*
+ * ------------------------------------------------------
+ *  Load any environment-specific settings from .env file
+ * ------------------------------------------------------
+ */
+
+// Load environment settings from .env files
+// into $_SERVER and $_ENV
+require BASEPATH.'Config/DotEnv.php';
+$env = new CodeIgniter\Config\DotEnv(APPPATH);
+$env->load();
+unset($env);
+
 /*
  * ------------------------------------------------------
  *  Load the framework constants
@@ -130,12 +118,45 @@ $loader->register();
 $loader->addNamespace('CodeIgniter', SUPPORTPATH);
 $loader->addNamespace('Config', SUPPORTPATH.'Config');
 
+/*
+ * ------------------------------------------------------
+ *  Load the global functions
+ * ------------------------------------------------------
+ */
+
+require_once BASEPATH.'Common.php';
+
+/*
+ * ------------------------------------------------------
+ *  Set custom exception handling
+ * ------------------------------------------------------
+ */
+$config = new \Config\App();
+
+Config\Services::exceptions($config, true)
+	->initialize();
+
 //--------------------------------------------------------------------
-// LOAD THE BOOTSTRAP FILE
+// Should we use a Composer autoloader?
 //--------------------------------------------------------------------
 
-$config = new Config\App();
-new CodeIgniter\MockBootstrap($config);
+if ($composer_autoload = $config->composerAutoload)
+{
+	if ($composer_autoload === TRUE)
+	{
+		file_exists(APPPATH.'vendor/autoload.php')
+			? require_once(APPPATH.'vendor/autoload.php')
+			: log_message('error', '$config->\'composerAutoload\' is set to TRUE but '.APPPATH.'vendor/autoload.php was not found.');
+	}
+	elseif (file_exists($composer_autoload))
+	{
+		require_once($composer_autoload);
+	}
+	else
+	{
+		log_message('error', 'Could not find the specified $config->\'composerAutoload\' path: '.$composer_autoload);
+	}
+}
 
 //--------------------------------------------------------------------
 // Load our TestCase