diff --git a/system/Autoloader/Autoloader.php b/system/Autoloader/Autoloader.php
index 4735119c85f9..3baf97fd3465 100644
--- a/system/Autoloader/Autoloader.php
+++ b/system/Autoloader/Autoloader.php
@@ -76,7 +76,6 @@
  */
 class Autoloader
 {
-
 	/**
 	 * Stores namespaces as key, and path as values.
 	 *
@@ -98,6 +97,8 @@ class Autoloader
 	 * the valid parts that we'll need.
 	 *
 	 * @param \Config\Autoload $config
+	 *
+	 * @return $this
 	 */
 	public function initialize(\Config\Autoload $config)
 	{
@@ -110,7 +111,7 @@ public function initialize(\Config\Autoload $config)
 
 		if (isset($config->psr4))
 		{
-			$this->prefixes = $config->psr4;
+			$this->addNamespace($config->psr4);
 		}
 
 		if (isset($config->classmap))
@@ -119,14 +120,14 @@ public function initialize(\Config\Autoload $config)
 		}
 
 		unset($config);
+
+		return $this;
 	}
 
 	//--------------------------------------------------------------------
 
 	/**
 	 * Register the loader with the SPL autoloader stack.
-	 *
-	 * @codeCoverageIgnore
 	 */
 	public function register()
 	{
@@ -144,41 +145,51 @@ public function register()
 		$config = is_array($this->classmap) ? $this->classmap : [];
 
 		spl_autoload_register(function ($class) use ($config) {
-			if (! array_key_exists($class, $config))
+			if (empty($config[$class]))
 			{
 				return false;
 			}
 
 			include_once $config[$class];
 		}, true, // Throw exception
-						   true // Prepend
+			true // Prepend
 		);
 	}
 
 	//--------------------------------------------------------------------
 
 	/**
-	 * Registers a namespace with the autoloader.
+	 * Registers namespaces with the autoloader.
 	 *
-	 * @param string $namespace
-	 * @param string $path
+	 * @param array|string $namespace
+	 * @param string       $path
 	 *
 	 * @return Autoloader
 	 */
-	public function addNamespace(string $namespace, string $path)
+	public function addNamespace($namespace, string $path = null)
 	{
-		if (isset($this->prefixes[$namespace]))
+		if (is_array($namespace))
 		{
-			if (is_string($this->prefixes[$namespace]))
+			foreach ($namespace as $prefix => $path)
 			{
-				$this->prefixes[$namespace] = [$this->prefixes[$namespace]];
-			}
+				$prefix = trim($prefix, '\\');
+
+				if (is_array($path))
+				{
+					foreach ($path as $dir)
+					{
+						$this->prefixes[$prefix][] = rtrim($dir, '/') . '/';
+					}
+
+					continue;
+				}
 
-			$this->prefixes[$namespace] = array_merge($this->prefixes[$namespace], [$path]);
+				$this->prefixes[$prefix][] = rtrim($path, '/') . '/';
+			}
 		}
 		else
 		{
-			$this->prefixes[$namespace] = [$path];
+			$this->prefixes[trim($namespace, '\\')][] = rtrim($path, '/') . '/';
 		}
 
 		return $this;
@@ -186,6 +197,27 @@ public function addNamespace(string $namespace, string $path)
 
 	//--------------------------------------------------------------------
 
+	/**
+	 * Get namespaces with prefixes as keys and paths as values.
+	 *
+	 * If a prefix param is set, returns only paths to the given prefix.
+	 *
+	 * @var string|null $prefix
+	 *
+	 * @return array
+	 */
+	public function getNamespace(string $prefix = null)
+	{
+		if ($prefix === null)
+		{
+			return $this->prefixes;
+		}
+
+		return $this->prefixes[trim($prefix, '\\')] ?? [];
+	}
+
+	//--------------------------------------------------------------------
+
 	/**
 	 * Removes a single namespace from the psr4 settings.
 	 *
@@ -195,7 +227,7 @@ public function addNamespace(string $namespace, string $path)
 	 */
 	public function removeNamespace(string $namespace)
 	{
-		unset($this->prefixes[$namespace]);
+		unset($this->prefixes[trim($namespace, '\\')]);
 
 		return $this;
 	}
@@ -207,7 +239,7 @@ public function removeNamespace(string $namespace)
 	 *
 	 * @param string $class The fully qualified class name.
 	 *
-	 * @return mixed            The mapped file on success, or boolean false
+	 * @return string|false The mapped file on success, or boolean false
 	 *                          on failure.
 	 */
 	public function loadClass(string $class)
@@ -234,7 +266,7 @@ public function loadClass(string $class)
 	 *
 	 * @param string $class The fully-qualified class name
 	 *
-	 * @return mixed            The mapped file name on success, or boolean false on fail
+	 * @return string|false The mapped file name on success, or boolean false on fail
 	 */
 	protected function loadInNamespace(string $class)
 	{
@@ -245,18 +277,14 @@ protected function loadInNamespace(string $class)
 
 		foreach ($this->prefixes as $namespace => $directories)
 		{
-			if (is_string($directories))
-			{
-				$directories = [$directories];
-			}
-
 			foreach ($directories as $directory)
 			{
 				$directory = rtrim($directory, '/');
 
 				if (strpos($class, $namespace) === 0)
 				{
-					$filePath = $directory . str_replace('\\', '/', substr($class, strlen($namespace))) . '.php';
+					$filePath = $directory . str_replace('\\', '/',
+							substr($class, strlen($namespace))) . '.php';
 					$filename = $this->requireFile($filePath);
 
 					if ($filename)
@@ -316,11 +344,9 @@ protected function loadLegacy(string $class)
 	 * A central way to require a file is loaded. Split out primarily
 	 * for testing purposes.
 	 *
-	 * @codeCoverageIgnore
-	 *
 	 * @param string $file
 	 *
-	 * @return boolean
+	 * @return string|false The filename on success, false if the file is not loaded
 	 */
 	protected function requireFile(string $file)
 	{
@@ -365,6 +391,5 @@ public function sanitizeFilename(string $filename): string
 
 		return $filename;
 	}
-
 	//--------------------------------------------------------------------
 }
diff --git a/system/Autoloader/FileLocator.php b/system/Autoloader/FileLocator.php
index fb2893f7c91b..05f65f62ce30 100644
--- a/system/Autoloader/FileLocator.php
+++ b/system/Autoloader/FileLocator.php
@@ -36,10 +36,8 @@
  * @filesource
  */
 
-use Config\Autoload;
-
 /**
- * Class Loader
+ * Class FileLocator
  *
  * Allows loading non-class files in a namespaced manner.
  * Works with Helpers, Views, etc.
@@ -48,29 +46,21 @@
  */
 class FileLocator
 {
-
 	/**
-	 * Stores our namespaces
-	 *
-	 * @var array
+	 * @var \CodeIgniter\Autoloader\Autoloader
 	 */
-	protected $namespaces;
+	protected $autoloader;
 
 	//--------------------------------------------------------------------
 
 	/**
 	 * Constructor
 	 *
-	 * @param Autoload $autoload
+	 * @param Autoloader $autoloader
 	 */
-	public function __construct(Autoload $autoload)
+	public function __construct(Autoloader $autoloader)
 	{
-		$this->namespaces = $autoload->psr4;
-
-		unset($autoload);
-
-		// Always keep the Application directory as a "package".
-		array_unshift($this->namespaces, APPPATH);
+		$this->autoloader = $autoloader;
 	}
 
 	//--------------------------------------------------------------------
@@ -83,27 +73,26 @@ public function __construct(Autoload $autoload)
 	 * @param string $folder The folder within the namespace that we should look for the file.
 	 * @param string $ext    The file extension the file should have.
 	 *
-	 * @return string       The path to the file if found, or an empty string.
+	 * @return string|false The path to the file, or false if not found.
 	 */
-	public function locateFile(string $file, string $folder = null, string $ext = 'php'): string
+	public function locateFile(string $file, string $folder = null, string $ext = 'php')
 	{
-		// Ensure the extension is on the filename
-		$file = strpos($file, '.' . $ext) !== false ? $file : $file . '.' . $ext;
+		$file = $this->ensureExt($file, $ext);
 
-		// Clean the folder name from the filename
-		if (! empty($folder))
+		// Clears the folder name if it is at the beginning of the filename
+		if (! empty($folder) && ($pos = strpos($file, $folder)) === 0)
 		{
-			$file = str_replace($folder . '/', '', $file);
+			$file = substr($file, strlen($folder . '/'));
 		}
 
-		// No namespaceing? Try the application folder.
+		// Is not namespaced? Try the application folder.
 		if (strpos($file, '\\') === false)
 		{
 			return $this->legacyLocate($file, $folder);
 		}
 
 		// Standardize slashes to handle nested directories.
-		$file = str_replace('/', '\\', $file);
+		$file = strtr($file, '/', '\\');
 
 		$segments = explode('\\', $file);
 
@@ -117,16 +106,20 @@ public function locateFile(string $file, string $folder = null, string $ext = 'p
 		$prefix   = '';
 		$filename = '';
 
+		// Namespaces always comes with arrays of paths
+		$namespaces = $this->autoloader->getNamespace();
+
 		while (! empty($segments))
 		{
-			$prefix .= empty($prefix) ? ucfirst(array_shift($segments)) : '\\' . ucfirst(array_shift($segments));
+			$prefix .= empty($prefix)
+				? ucfirst(array_shift($segments))
+				: '\\' . ucfirst(array_shift($segments));
 
-			if (! array_key_exists($prefix, $this->namespaces))
+			if (empty($namespaces[$prefix]))
 			{
 				continue;
 			}
-
-			$path     = $this->namespaces[$prefix] . '/';
+			$path     = $this->getNamespaces($prefix);
 			$filename = implode('/', $segments);
 			break;
 		}
@@ -134,19 +127,14 @@ public function locateFile(string $file, string $folder = null, string $ext = 'p
 		// IF we have a folder name, then the calling function
 		// expects this file to be within that folder, like 'Views',
 		// or 'libraries'.
-		if (! empty($folder) && strpos($filename, $folder) === false)
+		if (! empty($folder) && strpos($path . $filename, '/' . $folder . '/') === false)
 		{
 			$filename = $folder . '/' . $filename;
 		}
 
 		$path .= $filename;
 
-		if (! $this->requireFile($path))
-		{
-			$path = '';
-		}
-
-		return $path;
+		return is_file($path) ? $path : false;
 	}
 
 	//--------------------------------------------------------------------
@@ -224,18 +212,15 @@ public function getClassname(string $file) : string
 	 */
 	public function search(string $path, string $ext = 'php'): array
 	{
-		$foundPaths = [];
+		$path = $this->ensureExt($path, $ext);
 
-		// Ensure the extension is on the filename
-		$path = strpos($path, '.' . $ext) !== false ? $path : $path . '.' . $ext;
+		$foundPaths = [];
 
-		foreach ($this->namespaces as $name => $folder)
+		foreach ($this->getNamespaces() as $namespace)
 		{
-			$folder = rtrim($folder, '/') . '/';
-
-			if (is_file($folder . $path) === true)
+			if (is_file($namespace['path'] . $path))
 			{
-				$foundPaths[] = $folder . $path;
+				$foundPaths[] = $namespace['path'] . $path;
 			}
 		}
 
@@ -248,13 +233,69 @@ public function search(string $path, string $ext = 'php'): array
 	//--------------------------------------------------------------------
 
 	/**
-	 * Attempts to load a file and instantiate a new class by looking
-	 * at its full path and comparing that to our existing psr4 namespaces
-	 * in Autoloader config file.
+	 * Ensures a extension is at the end of a filename
+	 *
+	 * @param string $path
+	 * @param string $ext
+	 *
+	 * @return string
+	 */
+	protected function ensureExt(string $path, string $ext): string
+	{
+		if ($ext)
+		{
+			$ext = '.' . $ext;
+
+			if (substr($path, -strlen($ext)) !== $ext)
+			{
+				$path .= $ext;
+			}
+		}
+
+		return $path;
+	}
+
+	//--------------------------------------------------------------------
+
+	/**
+	 * @param string|null $prefix
+	 *
+	 * @return array|string
+	 */
+	protected function getNamespaces(string $prefix = null)
+	{
+		if ($prefix)
+		{
+			$path = $this->autoloader->getNamespace($prefix);
+
+			return isset($path[0]) ? $path[0] : '';
+		}
+
+		$namespaces = [];
+
+		foreach ($this->autoloader->getNamespace() as $prefix => $paths)
+		{
+			foreach ($paths as $path)
+			{
+				$namespaces[] = [
+					'prefix' => $prefix,
+					'path'   => $path,
+				];
+			}
+		}
+
+		return $namespaces;
+	}
+
+	//--------------------------------------------------------------------
+
+	/**
+	 * Find the qualified name of a file according to
+	 * the namespace of the first matched namespace path.
 	 *
 	 * @param string $path
 	 *
-	 * @return string|void
+	 * @return string|false The qualified name or false if the path is not found
 	 */
 	public function findQualifiedNameFromPath(string $path)
 	{
@@ -262,34 +303,39 @@ public function findQualifiedNameFromPath(string $path)
 
 		if (! $path)
 		{
-			return;
+			return false;
 		}
 
-		foreach ($this->namespaces as $namespace => $nsPath)
+		foreach ($this->getNamespaces() as $namespace)
 		{
-			$nsPath = realpath($nsPath);
-			if (is_numeric($namespace) || empty($nsPath))
+			$namespace['path'] = realpath($namespace['path']);
+
+			if (empty($namespace['path']))
 			{
 				continue;
 			}
 
-			if (mb_strpos($path, $nsPath) === 0)
+			if (mb_strpos($path, $namespace['path']) === 0)
 			{
-				$className = '\\' . $namespace . '\\' .
-						ltrim(str_replace('/', '\\', mb_substr($path, mb_strlen($nsPath))), '\\');
+				$className = '\\' . $namespace['prefix'] . '\\' .
+						ltrim(str_replace('/', '\\', mb_substr(
+							$path, mb_strlen($namespace['path']))
+						), '\\');
 				// Remove the file extension (.php)
 				$className = mb_substr($className, 0, -4);
 
 				return $className;
 			}
 		}
+
+		return false;
 	}
 
 	//--------------------------------------------------------------------
 
 	/**
 	 * Scans the defined namespaces, returning a list of all files
-	 * that are contained within the subpath specifed by $path.
+	 * that are contained within the subpath specified by $path.
 	 *
 	 * @param string $path
 	 *
@@ -305,9 +351,9 @@ public function listFiles(string $path): array
 		$files = [];
 		helper('filesystem');
 
-		foreach ($this->namespaces as $namespace => $nsPath)
+		foreach ($this->getNamespaces() as $namespace)
 		{
-			$fullPath = realpath(rtrim($nsPath, '/') . '/' . $path);
+			$fullPath = realpath($namespace['path'] . $path);
 
 			if (! is_dir($fullPath))
 			{
@@ -325,6 +371,8 @@ public function listFiles(string $path): array
 		return $files;
 	}
 
+	//--------------------------------------------------------------------
+
 	/**
 	 * Checks the application folder to see if the file can be found.
 	 * Only for use with filenames that DO NOT include namespacing.
@@ -332,10 +380,9 @@ public function listFiles(string $path): array
 	 * @param string      $file
 	 * @param string|null $folder
 	 *
-	 * @return   string
-	 * @internal param string $ext
+	 * @return string|false The path to the file, or false if not found.
 	 */
-	protected function legacyLocate(string $file, string $folder = null): string
+	protected function legacyLocate(string $file, string $folder = null)
 	{
 		$paths = [
 			APPPATH,
@@ -346,30 +393,12 @@ protected function legacyLocate(string $file, string $folder = null): string
 		{
 			$path .= empty($folder) ? $file : $folder . '/' . $file;
 
-			if ($this->requireFile($path) === true)
+			if (is_file($path))
 			{
 				return $path;
 			}
 		}
 
-		return '';
-	}
-
-	//--------------------------------------------------------------------
-
-	/**
-	 * Checks to see if a file exists on the file system. This is split
-	 * out to it's own method to make testing simpler.
-	 *
-	 * @codeCoverageIgnore
-	 * @param              string $path
-	 *
-	 * @return boolean
-	 */
-	protected function requireFile(string $path): bool
-	{
-		return is_file($path);
+		return false;
 	}
-
-	//--------------------------------------------------------------------
 }
diff --git a/system/CLI/CommandRunner.php b/system/CLI/CommandRunner.php
index 7585aa9fd97f..bca09800090a 100644
--- a/system/CLI/CommandRunner.php
+++ b/system/CLI/CommandRunner.php
@@ -37,6 +37,7 @@
  * @filesource
  */
 
+use CodeIgniter\Config\Services;
 use CodeIgniter\Controller;
 
 class CommandRunner extends Controller
@@ -109,7 +110,7 @@ protected function runCommand(string $command, array $params)
 	{
 		if (! isset($this->commands[$command]))
 		{
-			CLI::error('Command \'' . $command . '\' not found');
+			CLI::error(lang('CLI.commandNotFound', [$command]));
 			CLI::newLine();
 			return;
 		}
@@ -127,12 +128,10 @@ protected function runCommand(string $command, array $params)
 	/**
 	 * Scans all Commands directories and prepares a list
 	 * of each command with it's group and file.
-	 *
-	 * @return null|void
 	 */
 	protected function createCommandList()
 	{
-		$files = service('locator')->listFiles('Commands/');
+		$files = Services::locator()->listFiles('Commands/');
 
 		// If no matching command files were found, bail
 		if (empty($files))
@@ -144,7 +143,7 @@ protected function createCommandList()
 		// alias exists in the class. If so, return it. Otherwise, try the next.
 		foreach ($files as $file)
 		{
-			$className = service('locator')->findQualifiedNameFromPath($file);
+			$className = Services::locator()->findQualifiedNameFromPath($file);
 			if (empty($className) || ! class_exists($className))
 			{
 				continue;
diff --git a/system/Common.php b/system/Common.php
index 1814c882d4dd..c9cbadfc81af 100644
--- a/system/Common.php
+++ b/system/Common.php
@@ -199,7 +199,7 @@ function env(string $key, $default = null)
 			case 'empty':
 				return '';
 			case 'null':
-				return;
+				return null;
 		}
 
 		return $value;
@@ -488,9 +488,7 @@ function is_cli()
 	 */
 	function route_to(string $method, ...$params): string
 	{
-		$routes = Services::routes();
-
-		return $routes->reverseRoute($method, ...$params);
+		return Services::routes()->reverseRoute($method, ...$params);
 	}
 }
 
@@ -713,7 +711,7 @@ function csrf_field()
 	 *
 	 * Not testable, as it will exit!
 	 *
-	 * @throws             \CodeIgniter\HTTP\RedirectException
+	 * @throws             \CodeIgniter\HTTP\Exceptions\HTTPException
 	 * @codeCoverageIgnore
 	 */
 	function force_https(int $duration = 31536000, RequestInterface $request = null, ResponseInterface $response = null)
diff --git a/system/Config/BaseService.php b/system/Config/BaseService.php
index 4da15189cb0f..a9e5bba74057 100644
--- a/system/Config/BaseService.php
+++ b/system/Config/BaseService.php
@@ -118,6 +118,31 @@ protected static function getSharedInstance(string $key, ...$params)
 
 	//--------------------------------------------------------------------
 
+	/**
+	 * The Autoloader class is the central class that handles our
+	 * spl_autoload_register method, and helper methods.
+	 *
+	 * @param boolean $getShared
+	 *
+	 * @return \CodeIgniter\Autoloader\Autoloader
+	 */
+	public static function autoloader(bool $getShared = true)
+	{
+		if ($getShared)
+		{
+			if (empty(static::$instances['autoloader']))
+			{
+				static::$instances['autoloader'] = new \CodeIgniter\Autoloader\Autoloader();
+			}
+
+			return static::$instances['autoloader'];
+		}
+
+		return new \CodeIgniter\Autoloader\Autoloader();
+	}
+
+	//--------------------------------------------------------------------
+
 	/**
 	 * The file locator provides utility methods for looking for non-classes
 	 * within namespaced folders, as well as convenience methods for
@@ -131,10 +156,17 @@ public static function locator(bool $getShared = true)
 	{
 		if ($getShared)
 		{
-			return static::getSharedInstance('locator');
+			if (empty(static::$instances['locator']))
+			{
+				static::$instances['locator'] = new \CodeIgniter\Autoloader\FileLocator(
+					static::autoloader()
+				);
+			}
+
+			return static::$instances['locator'];
 		}
 
-		return new \CodeIgniter\Autoloader\FileLocator(new \Config\Autoload());
+		return new \CodeIgniter\Autoloader\FileLocator(static::autoloader());
 	}
 
 	//--------------------------------------------------------------------
@@ -164,12 +196,19 @@ public static function __callStatic(string $name, array $arguments)
 
 	/**
 	 * Reset shared instances and mocks for testing.
+	 *
+	 * @param boolean $init_autoloader Initializes autoloader instance
 	 */
-	public static function reset()
+	public static function reset(bool $init_autoloader = false)
 	{
 		static::$mocks = [];
 
 		static::$instances = [];
+
+		if ($init_autoloader)
+		{
+			static::autoloader()->initialize(new \Config\Autoload());
+		}
 	}
 
 	//--------------------------------------------------------------------
@@ -196,6 +235,8 @@ public static function injectMock(string $name, $mock)
 	 *
 	 * @param string $name
 	 * @param array  $arguments
+	 *
+	 * @return mixed
 	 */
 	protected static function discoverServices(string $name, array $arguments)
 	{
@@ -210,7 +251,7 @@ protected static function discoverServices(string $name, array $arguments)
 
 				if (empty($files))
 				{
-					return;
+					return null;
 				}
 
 				// Get instances of all service classes and cache them locally.
@@ -230,7 +271,7 @@ protected static function discoverServices(string $name, array $arguments)
 
 		if (! static::$services)
 		{
-			return;
+			return null;
 		}
 
 		// Try to find the desired service method
@@ -241,5 +282,7 @@ protected static function discoverServices(string $name, array $arguments)
 				return $class::$name(...$arguments);
 			}
 		}
+
+		return null;
 	}
 }
diff --git a/system/Config/Services.php b/system/Config/Services.php
index 7f724037b7b9..e9cd8f96735c 100644
--- a/system/Config/Services.php
+++ b/system/Config/Services.php
@@ -60,26 +60,6 @@
  */
 class Services extends BaseService
 {
-	/**
-	 * The Autoloader class is the central class that handles our
-	 * spl_autoload_register method, and helper methods.
-	 *
-	 * @param boolean $getShared
-	 *
-	 * @return \CodeIgniter\Autoloader\Autoloader
-	 */
-	public static function autoloader(bool $getShared = true)
-	{
-		if ($getShared)
-		{
-			return static::getSharedInstance('autoloader');
-		}
-
-		return new \CodeIgniter\Autoloader\Autoloader();
-	}
-
-	//--------------------------------------------------------------------
-
 	/**
 	 * The cache class provides a simple way to store and retrieve
 	 * complex data for later.
diff --git a/system/Language/Language.php b/system/Language/Language.php
index 667182f66fc7..35f54bfa4dc4 100644
--- a/system/Language/Language.php
+++ b/system/Language/Language.php
@@ -36,6 +36,13 @@
  * @filesource
  */
 
+use CodeIgniter\Config\Services;
+
+/**
+ * Class Language
+ *
+ * @package CodeIgniter\Language
+ */
 class Language
 {
 
@@ -102,6 +109,18 @@ public function setLocale(string $locale = null)
 		return $this;
 	}
 
+	//--------------------------------------------------------------------
+
+	/**
+	 * @return string
+	 */
+	public function getLocale(): string
+	{
+		return $this->locale;
+	}
+
+	//--------------------------------------------------------------------
+
 	/**
 	 * Parses the language string for a file, loads the file, if necessary,
 	 * getting the line.
@@ -255,7 +274,7 @@ protected function load(string $file, string $locale, bool $return = false)
 	 */
 	protected function requireFile(string $path): array
 	{
-		$files = service('locator')->search($path);
+		$files = Services::locator()->search($path);
 
 		$strings = [];
 
diff --git a/system/Language/en/CLI.php b/system/Language/en/CLI.php
index 40bc70332028..4f6176e3d9dd 100644
--- a/system/Language/en/CLI.php
+++ b/system/Language/en/CLI.php
@@ -15,6 +15,7 @@
  */
 
 return [
+   'commandNotFound' => 'Command "{0}" not found.',
    'helpUsage'       => 'Usage:',
    'helpDescription' => 'Description:',
    'helpOptions'     => 'Options:',
diff --git a/system/Log/Logger.php b/system/Log/Logger.php
index aeb0ab0791c2..983c1d3e2c0a 100644
--- a/system/Log/Logger.php
+++ b/system/Log/Logger.php
@@ -146,8 +146,8 @@ class Logger implements LoggerInterface
 	/**
 	 * Constructor.
 	 *
-	 * @param  type    $config
-	 * @param  boolean $debug
+	 * @param  \Config\Logger $config
+	 * @param  boolean        $debug
 	 * @throws \RuntimeException
 	 */
 	public function __construct($config, bool $debug = CI_DEBUG)
@@ -194,11 +194,11 @@ public function __construct($config, bool $debug = CI_DEBUG)
 	 * @param string $message
 	 * @param array  $context
 	 *
-	 * @return null
+	 * @return boolean
 	 */
 	public function emergency($message, array $context = [])
 	{
-		$this->log('emergency', $message, $context);
+		return $this->log('emergency', $message, $context);
 	}
 
 	//--------------------------------------------------------------------
@@ -212,11 +212,11 @@ public function emergency($message, array $context = [])
 	 * @param string $message
 	 * @param array  $context
 	 *
-	 * @return null
+	 * @return boolean
 	 */
 	public function alert($message, array $context = [])
 	{
-		$this->log('alert', $message, $context);
+		return $this->log('alert', $message, $context);
 	}
 
 	//--------------------------------------------------------------------
@@ -229,11 +229,11 @@ public function alert($message, array $context = [])
 	 * @param string $message
 	 * @param array  $context
 	 *
-	 * @return null
+	 * @return boolean
 	 */
 	public function critical($message, array $context = [])
 	{
-		$this->log('critical', $message, $context);
+		return $this->log('critical', $message, $context);
 	}
 
 	//--------------------------------------------------------------------
@@ -245,11 +245,11 @@ public function critical($message, array $context = [])
 	 * @param string $message
 	 * @param array  $context
 	 *
-	 * @return null
+	 * @return boolean
 	 */
 	public function error($message, array $context = [])
 	{
-		$this->log('error', $message, $context);
+		return $this->log('error', $message, $context);
 	}
 
 	//--------------------------------------------------------------------
@@ -263,11 +263,11 @@ public function error($message, array $context = [])
 	 * @param string $message
 	 * @param array  $context
 	 *
-	 * @return null
+	 * @return boolean
 	 */
 	public function warning($message, array $context = [])
 	{
-		$this->log('warning', $message, $context);
+		return $this->log('warning', $message, $context);
 	}
 
 	//--------------------------------------------------------------------
@@ -278,11 +278,11 @@ public function warning($message, array $context = [])
 	 * @param string $message
 	 * @param array  $context
 	 *
-	 * @return null
+	 * @return boolean
 	 */
 	public function notice($message, array $context = [])
 	{
-		$this->log('notice', $message, $context);
+		return $this->log('notice', $message, $context);
 	}
 
 	//--------------------------------------------------------------------
@@ -295,11 +295,11 @@ public function notice($message, array $context = [])
 	 * @param string $message
 	 * @param array  $context
 	 *
-	 * @return null
+	 * @return boolean
 	 */
 	public function info($message, array $context = [])
 	{
-		$this->log('info', $message, $context);
+		return $this->log('info', $message, $context);
 	}
 
 	//--------------------------------------------------------------------
@@ -310,11 +310,11 @@ public function info($message, array $context = [])
 	 * @param string $message
 	 * @param array  $context
 	 *
-	 * @return null
+	 * @return boolean
 	 */
 	public function debug($message, array $context = [])
 	{
-		$this->log('debug', $message, $context);
+		return $this->log('debug', $message, $context);
 	}
 
 	//--------------------------------------------------------------------
diff --git a/tests/_support/Autoloader/MockAutoloader.php b/tests/_support/Autoloader/MockAutoloader.php
deleted file mode 100644
index 8a722a571235..000000000000
--- a/tests/_support/Autoloader/MockAutoloader.php
+++ /dev/null
@@ -1,25 +0,0 @@
-<?php namespace Tests\Support\Autoloader;
-
-use CodeIgniter\Autoloader\Autoloader;
-
-class MockAutoloader extends Autoloader
-{
-
-	protected $files = [];
-
-	//--------------------------------------------------------------------
-
-	public function setFiles($files)
-	{
-		$this->files = $files;
-	}
-
-	//--------------------------------------------------------------------
-
-	protected function requireFile(string $file)
-	{
-		return in_array($file, $this->files) ? $file : false;
-	}
-
-	//--------------------------------------------------------------------
-}
diff --git a/tests/_support/Autoloader/MockFileLocator.php b/tests/_support/Autoloader/MockFileLocator.php
deleted file mode 100644
index c683bbb9d8c6..000000000000
--- a/tests/_support/Autoloader/MockFileLocator.php
+++ /dev/null
@@ -1,25 +0,0 @@
-<?php namespace Tests\Support\Autoloader;
-
-use CodeIgniter\Autoloader\FileLocator;
-
-class MockFileLocator extends FileLocator
-{
-
-	protected $files = [];
-
-	//--------------------------------------------------------------------
-
-	public function setFiles($files)
-	{
-		$this->files = $files;
-	}
-
-	//--------------------------------------------------------------------
-
-	protected function requireFile(string $file): bool
-	{
-		return in_array($file, $this->files) ? $file : false;
-	}
-
-	//--------------------------------------------------------------------
-}
diff --git a/tests/_support/Autoloader/UnnamespacedClass.php b/tests/_support/Autoloader/UnnamespacedClass.php
new file mode 100644
index 000000000000..67b1ed352b42
--- /dev/null
+++ b/tests/_support/Autoloader/UnnamespacedClass.php
@@ -0,0 +1,5 @@
+<?php
+
+class UnnamespacedClass
+{
+}
diff --git a/tests/system/Autoloader/AutoloaderTest.php b/tests/system/Autoloader/AutoloaderTest.php
index 5e1b025a60d8..3d9dca4738a6 100644
--- a/tests/system/Autoloader/AutoloaderTest.php
+++ b/tests/system/Autoloader/AutoloaderTest.php
@@ -1,15 +1,16 @@
 <?php namespace CodeIgniter\Autoloader;
 
 use Config\Autoload;
-use Tests\Support\Autoloader\MockAutoloader;
-
-//--------------------------------------------------------------------
 
 class AutoloaderTest extends \CIUnitTestCase
 {
-
+	/**
+	 * @var \CodeIgniter\Autoloader\Autoloader
+	 */
 	protected $loader;
 
+	protected $filesPath = SUPPORTPATH . 'Autoloader/';
+
 	//--------------------------------------------------------------------
 
 	public function setUp()
@@ -19,30 +20,35 @@ public function setUp()
 		$config = new Autoload();
 
 		$config->classmap = [
-			'FirstClass'        => '/app/dir/First.php',
-			'Name\Spaced\Class' => '/app/namespace/Class.php',
+			'UnnamespacedClass' => SUPPORTPATH . 'Autoloader/UnnamespacedClass.php',
+			'OtherClass'        => APPPATH . 'Controllers/Home.php',
+			'Name\Spaced\Class' => APPPATH . 'Controllers/Home.php',
 		];
 		$config->psr4     = [
-			'App\Controllers' => '/application/Controllers',
-			'App\Libraries'   => '/application/somewhere',
+			'App'         => APPPATH,
+			'CodeIgniter' => BASEPATH,
 		];
 
-		$this->loader = new MockAutoloader();
-		$this->loader->initialize($config);
+		$this->loader = new Autoloader();
+		$this->loader->initialize($config)->register();
+	}
 
-		$this->loader->setFiles([
-			'/application/Controllers/Classname.php',
-			'/application/somewhere/Classname.php',
-			'/app/dir/First.php',
-			'/app/namespace/Class.php',
-			'/my/app/Class.php',
-			APPPATH . 'Libraries/someLibrary.php',
-			APPPATH . 'Models/someModel.php',
-			APPPATH . 'Models/Some/CoolModel.php',
-		]);
+	public function testLoadStoredClass()
+	{
+		$this->assertInstanceOf('UnnamespacedClass', new \UnnamespacedClass());
+	}
+
+	public function testInitializeWithInvalidArguments()
+	{
+		$this->expectException(\InvalidArgumentException::class);
+
+		$config           = new Autoload();
+		$config->classmap = [];
+		$config->psr4     = [];
+
+		(new Autoloader())->initialize($config);
 	}
 
-	//--------------------------------------------------------------------
 	//--------------------------------------------------------------------
 	// PSR4 Namespacing
 	//--------------------------------------------------------------------
@@ -75,12 +81,12 @@ public function testServiceAutoLoader()
 
 	public function testExistingFile()
 	{
-		$actual   = $this->loader->loadClass('App\Controllers\Classname');
-		$expected = '/application/Controllers/Classname.php';
+		$actual   = $this->loader->loadClass('App\Controllers\Home');
+		$expected = APPPATH . 'Controllers/Home.php';
 		$this->assertSame($expected, $actual);
 
-		$actual   = $this->loader->loadClass('App\Libraries\Classname');
-		$expected = '/application/somewhere/Classname.php';
+		$actual   = $this->loader->loadClass('CodeIgniter\Helpers\array_helper');
+		$expected = BASEPATH . 'Helpers/array_helper.php';
 		$this->assertSame($expected, $actual);
 	}
 
@@ -88,8 +94,8 @@ public function testExistingFile()
 
 	public function testMatchesWithPreceedingSlash()
 	{
-		$actual   = $this->loader->loadClass('\App\Controllers\Classname');
-		$expected = '/application/Controllers/Classname.php';
+		$actual   = $this->loader->loadClass('\App\Controllers\Home');
+		$expected = APPPATH . 'Controllers/Home.php';
 		$this->assertSame($expected, $actual);
 	}
 
@@ -97,8 +103,8 @@ public function testMatchesWithPreceedingSlash()
 
 	public function testMatchesWithFileExtension()
 	{
-		$actual   = $this->loader->loadClass('\App\Controllers\Classname.php');
-		$expected = '/application/Controllers/Classname.php';
+		$actual   = $this->loader->loadClass('\App\Controllers\Home.php');
+		$expected = APPPATH . 'Controllers/Home.php';
 		$this->assertSame($expected, $actual);
 	}
 
@@ -109,7 +115,6 @@ public function testMissingFile()
 		$this->assertFalse($this->loader->loadClass('\App\Missing\Classname'));
 	}
 
-	//--------------------------------------------------------------------
 	//--------------------------------------------------------------------
 
 	/**
@@ -122,7 +127,7 @@ public function testInitializeException()
 		$config->classmap = [];
 		$config->psr4     = [];
 
-		$this->loader = new MockAutoloader();
+		$this->loader = new Autoloader();
 		$this->loader->initialize($config);
 	}
 
@@ -130,48 +135,47 @@ public function testAddNamespaceWorks()
 	{
 		$this->assertFalse($this->loader->loadClass('My\App\Class'));
 
-		$this->loader->addNamespace('My\App', '/my/app');
+		$this->loader->addNamespace('My\App', __DIR__);
 
-		$actual   = $this->loader->loadClass('My\App\Class');
-		$expected = '/my/app/Class.php';
+		$actual   = $this->loader->loadClass('My\App\AutoloaderTest');
+		$expected = __FILE__;
 
 		$this->assertSame($expected, $actual);
 	}
 
 	public function testAddNamespaceMultiplePathsWorks()
 	{
-		$this->loader->addNamespace('My\App', '/my/app');
-		$this->loader->addNamespace('My\App', '/test/app');
-		$this->loader->setFiles([
-			'/my/app/Class.php',
-			'/test/app/ClassTest.php',
-		]);
+		$this->loader->addNamespace('My\App', APPPATH . 'Config');
+		$this->loader->addNamespace('My\App', __DIR__);
 
-		$actual   = $this->loader->loadClass('My\App\ClassTest');
-		$expected = '/test/app/ClassTest.php';
+		$actual   = $this->loader->loadClass('My\App\App');
+		$expected = APPPATH . 'Config/App.php';
 		$this->assertSame($expected, $actual);
 
-		$actual   = $this->loader->loadClass('My\App\Class');
-		$expected = '/my/app/Class.php';
+		$actual   = $this->loader->loadClass('My\App\AutoloaderTest');
+		$expected = __FILE__;
 		$this->assertSame($expected, $actual);
 	}
 
-	public function testAddNamespaceStingToArray()
+	public function testAddNamespaceStringToArray()
 	{
-		$this->loader->addNamespace('App\Controllers', '/application/Controllers');
+		$this->loader->addNamespace('App\Controllers', __DIR__);
 
-		$this->assertSame('/application/Controllers/Classname.php', $this->loader->loadClass('App\Controllers\Classname'));
+		$this->assertSame(
+			__FILE__,
+			$this->loader->loadClass('App\Controllers\AutoloaderTest')
+		);
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testRemoveNamespace()
 	{
-		$this->loader->addNamespace('My\App', '/my/app');
-		$this->assertSame('/my/app/Class.php', $this->loader->loadClass('My\App\Class'));
+		$this->loader->addNamespace('My\App', __DIR__);
+		$this->assertSame(__FILE__, $this->loader->loadClass('My\App\AutoloaderTest'));
 
 		$this->loader->removeNamespace('My\App');
-		$this->assertFalse((bool) $this->loader->loadClass('My\App\Class'));
+		$this->assertFalse((bool) $this->loader->loadClass('My\App\AutoloaderTest'));
 	}
 
 	//--------------------------------------------------------------------
@@ -179,16 +183,14 @@ public function testRemoveNamespace()
 	public function testLoadLegacy()
 	{
 		// should not be able to find a folder
-		$this->assertFalse((bool) $this->loader->loadClass('someLibraries'));
-		// should be able to find these because we said so in the MockAutoloader
-		$this->assertTrue((bool) $this->loader->loadClass('someLibrary'));
-		$this->assertTrue((bool) $this->loader->loadClass('someModel'));
+		$this->assertFalse((bool) $this->loader->loadClass(__DIR__));
+		// should be able to find these because we said so in the Autoloader
+		$this->assertTrue((bool) $this->loader->loadClass('Home'));
 		// should not be able to find these - don't exist
 		$this->assertFalse((bool) $this->loader->loadClass('anotherLibrary'));
 		$this->assertFalse((bool) $this->loader->loadClass('\nester\anotherLibrary'));
-		$this->assertFalse((bool) $this->loader->loadClass('\Shouldnt\Find\This'));
 		// should not be able to find these legacy classes - namespaced
-		$this->assertFalse($this->loader->loadClass('\Some\CoolModel'));
+		$this->assertFalse($this->loader->loadClass('Controllers\Home'));
 	}
 
 	//--------------------------------------------------------------------
diff --git a/tests/system/Autoloader/FileLocatorTest.php b/tests/system/Autoloader/FileLocatorTest.php
index fddc7a085c9a..f9e55ca55657 100644
--- a/tests/system/Autoloader/FileLocatorTest.php
+++ b/tests/system/Autoloader/FileLocatorTest.php
@@ -1,15 +1,11 @@
 <?php namespace CodeIgniter\Autoloader;
 
-use Tests\Support\Config\MockAutoload;
-use Tests\Support\Autoloader\MockFileLocator;
-
 class FileLocatorTest extends \CIUnitTestCase
 {
-
 	/**
-	 * @var MockFileLocator
+	 * @var \CodeIgniter\Autoloader\FileLocator
 	 */
-	protected $loader;
+	protected $locator;
 
 	//--------------------------------------------------------------------
 
@@ -17,119 +13,136 @@ public function setUp()
 	{
 		parent::setUp();
 
-		$config       = new MockAutoload();
-		$config->psr4 = [
-			'App\Libraries' => '/application/somewhere',
-			'App'           => '/application',
-			'Sys'           => BASEPATH,
-			'Blog'          => '/modules/blog',
+		$autoloader = new Autoloader();
+		$autoloader->initialize(new \Config\Autoload());
+		$autoloader->addNamespace([
+			'Unknown'       => '/i/do/not/exist',
 			'Tests/Support' => TESTPATH . '_support/',
-		];
+			'App'           => APPPATH,
+			'CodeIgniter'   => [
+				BASEPATH,
+				TESTPATH,
+			],
+			'Errors'        => APPPATH . 'Views/errors',
+			'System'        => SUPPORTPATH . 'Autoloader/system',
+		]);
 
-		$this->loader = new MockFileLocator($config);
+		$this->locator = new FileLocator($autoloader);
+	}
 
-		$this->loader->setFiles([
-			APPPATH . 'index.php',
-			APPPATH . 'Views/index.php',
-			APPPATH . 'Views/admin/users/create.php',
-			'/modules/blog/Views/index.php',
-			'/modules/blog/Views/admin/posts.php',
-		]);
+	//--------------------------------------------------------------------
+
+	public function testLocateFileWorksWithLegacyStructure()
+	{
+		$file = 'Controllers/Home';
+
+		$expected = APPPATH . 'Controllers/Home.php';
+
+		$this->assertEquals($expected, $this->locator->locateFile($file));
+	}
+
+	//--------------------------------------------------------------------
+
+	public function testLocateFileWithLegacyStructureNotFound()
+	{
+		$file = 'Unknown';
+
+		$this->assertFalse($this->locator->locateFile($file));
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testLocateFileWorksInApplicationDirectory()
 	{
-		$file = 'index';
+		$file = 'welcome_message';
 
-		$expected = APPPATH . 'Views/index.php';
+		$expected = APPPATH . 'Views/welcome_message.php';
 
-		$this->assertEquals($expected, $this->loader->locateFile($file, 'Views'));
+		$this->assertEquals($expected, $this->locator->locateFile($file, 'Views'));
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testLocateFileWorksInApplicationDirectoryWithoutFolder()
 	{
-		$file = 'index';
+		$file = 'bootstrap';
 
-		$expected = APPPATH . 'index.php';
+		$expected = BASEPATH . 'bootstrap.php';
 
-		$this->assertEquals($expected, $this->loader->locateFile($file));
+		$this->assertEquals($expected, $this->locator->locateFile($file));
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testLocateFileWorksInNestedApplicationDirectory()
 	{
-		$file = 'admin/users/create';
+		$file = 'Controllers/Home';
 
-		$expected = APPPATH . 'Views/admin/users/create.php';
+		$expected = APPPATH . 'Controllers/Home.php';
 
-		$this->assertEquals($expected, $this->loader->locateFile($file, 'Views'));
+		$this->assertEquals($expected, $this->locator->locateFile($file, 'Controllers'));
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testLocateFileReplacesFolderName()
 	{
-		$file = '\Blog\Views/admin/posts.php';
+		$file = '\App\Views/errors/html/error_404.php';
 
-		$expected = '/modules/blog/Views/admin/posts.php';
+		$expected = APPPATH . 'Views/errors/html/error_404.php';
 
-		$this->assertEquals($expected, $this->loader->locateFile($file, 'Views'));
+		$this->assertEquals($expected, $this->locator->locateFile($file, 'Views'));
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testLocateFileReplacesFolderNameLegacy()
 	{
-		$file = 'Views/index.php';
+		$file = 'Views/welcome_message.php';
 
-		$expected = APPPATH . 'Views/index.php';
+		$expected = APPPATH . 'Views/welcome_message.php';
 
-		$this->assertEquals($expected, $this->loader->locateFile($file, 'Views'));
+		$this->assertEquals($expected, $this->locator->locateFile($file, 'Views'));
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testLocateFileCanFindNamespacedView()
 	{
-		$file = '\Blog\index';
+		$file = '\Errors\error_404';
 
-		$expected = '/modules/blog/Views/index.php';
+		$expected = APPPATH . 'Views/errors/html/error_404.php';
 
-		$this->assertEquals($expected, $this->loader->locateFile($file, 'Views'));
+		$this->assertEquals($expected, $this->locator->locateFile($file, 'html'));
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testLocateFileCanFindNestedNamespacedView()
 	{
-		$file = '\Blog\admin/posts.php';
+		$file = '\Errors\html/error_404';
 
-		$expected = '/modules/blog/Views/admin/posts.php';
+		$expected = APPPATH . 'Views/errors/html/error_404.php';
 
-		$this->assertEquals($expected, $this->loader->locateFile($file, 'Views'));
+		$this->assertEquals($expected, $this->locator->locateFile($file, 'html'));
 	}
 
 	//--------------------------------------------------------------------
 
-	public function testLocateFileReturnsEmptyWithBadNamespace()
+	public function testLocateFileNotFoundWithBadNamespace()
 	{
 		$file = '\Blogger\admin/posts.php';
 
-		$this->assertEquals('', $this->loader->locateFile($file, 'Views'));
+		$this->assertFalse($this->locator->locateFile($file, 'Views'));
 	}
 
 	//--------------------------------------------------------------------
 
 	public function testSearchSimple()
 	{
-		$expected = rtrim(APPPATH, '/') . '/Config/App.php';
+		$expected = APPPATH . 'Config/App.php';
 
-		$foundFiles = $this->loader->search('Config/App.php');
+		$foundFiles = $this->locator->search('Config/App.php');
 
 		$this->assertEquals($expected, $foundFiles[0]);
 	}
@@ -138,9 +151,9 @@ public function testSearchSimple()
 
 	public function testSearchWithFileExtension()
 	{
-		$expected = rtrim(APPPATH, '/') . '/Config/App.php';
+		$expected = APPPATH . 'Config/App.php';
 
-		$foundFiles = $this->loader->search('Config/App', 'php');
+		$foundFiles = $this->locator->search('Config/App', 'php');
 
 		$this->assertEquals($expected, $foundFiles[0]);
 	}
@@ -149,12 +162,12 @@ public function testSearchWithFileExtension()
 
 	public function testSearchWithMultipleFilesFound()
 	{
-		$foundFiles = $this->loader->search('index', 'html');
+		$foundFiles = $this->locator->search('index', 'html');
 
-		$expected = rtrim(APPPATH, '/') . '/index.html';
+		$expected = APPPATH . 'index.html';
 		$this->assertContains($expected, $foundFiles);
 
-		$expected = rtrim(BASEPATH, '/') . '/index.html';
+		$expected = BASEPATH . 'index.html';
 		$this->assertContains($expected, $foundFiles);
 	}
 
@@ -162,7 +175,7 @@ public function testSearchWithMultipleFilesFound()
 
 	public function testSearchForFileNotExist()
 	{
-		$foundFiles = $this->loader->search('Views/Fake.html');
+		$foundFiles = $this->locator->search('Views/Fake.html');
 
 		$this->assertArrayNotHasKey(0, $foundFiles);
 	}
@@ -171,7 +184,7 @@ public function testSearchForFileNotExist()
 
 	public function testListFilesSimple()
 	{
-		$files = $this->loader->listFiles('Config/');
+		$files = $this->locator->listFiles('Config/');
 
 		$expectedWin = APPPATH . 'Config\App.php';
 		$expectedLin = APPPATH . 'Config/App.php';
@@ -182,7 +195,7 @@ public function testListFilesSimple()
 
 	public function testListFilesWithFileAsInput()
 	{
-		$files = $this->loader->listFiles('Config/App.php');
+		$files = $this->locator->listFiles('Config/App.php');
 
 		$this->assertEmpty($files);
 	}
@@ -191,7 +204,7 @@ public function testListFilesWithFileAsInput()
 
 	public function testListFilesFromMultipleDir()
 	{
-		$files = $this->loader->listFiles('Filters/');
+		$files = $this->locator->listFiles('Filters/');
 
 		$expectedWin = APPPATH . 'Filters\DebugToolbar.php';
 		$expectedLin = APPPATH . 'Filters/DebugToolbar.php';
@@ -206,7 +219,7 @@ public function testListFilesFromMultipleDir()
 
 	public function testListFilesWithPathNotExist()
 	{
-		$files = $this->loader->listFiles('Fake/');
+		$files = $this->locator->listFiles('Fake/');
 
 		$this->assertEmpty($files);
 	}
@@ -215,38 +228,47 @@ public function testListFilesWithPathNotExist()
 
 	public function testListFilesWithoutPath()
 	{
-		$files = $this->loader->listFiles('');
+		$files = $this->locator->listFiles('');
 
 		$this->assertEmpty($files);
 	}
 
 	public function testFindQNameFromPathSimple()
 	{
-		$ClassName = $this->loader->findQualifiedNameFromPath('system/HTTP/Header.php');
-		$expected  = '\Sys\HTTP\Header';
+		$ClassName = $this->locator->findQualifiedNameFromPath(BASEPATH . 'HTTP/Header.php');
+		$expected  = '\CodeIgniter\HTTP\Header';
 
 		$this->assertEquals($expected, $ClassName);
 	}
 
-	public function testFindQNameFromPathWithNumericNamespace()
+	public function testFindQNameFromPathWithFileNotExist()
 	{
-		$ClassName = $this->loader->findQualifiedNameFromPath('application/Config/App.php');
+		$ClassName = $this->locator->findQualifiedNameFromPath('modules/blog/Views/index.php');
 
-		$this->assertNull($ClassName);
+		$this->assertFalse($ClassName);
 	}
 
-	public function testFindQNameFromPathWithFileNotExist()
+	public function testFindQNameFromPathWithoutCorrespondingNamespace()
 	{
-		$ClassName = $this->loader->findQualifiedNameFromPath('modules/blog/Views/index.php');
+		$ClassName = $this->locator->findQualifiedNameFromPath('/etc/hosts');
 
-		$this->assertNull($ClassName);
+		$this->assertFalse($ClassName);
 	}
 
-	public function testFindQNameFromPathWithoutCorrespondingNamespace()
+	public function testGetClassNameFromClassFile()
 	{
-		$ClassName = $this->loader->findQualifiedNameFromPath('tests/system/CodeIgniterTest.php');
+		$this->assertEquals(
+			__CLASS__,
+			$this->locator->getClassname(__FILE__)
+		);
+	}
 
-		$this->assertNull($ClassName);
+	public function testGetClassNameFromNonClassFile()
+	{
+		$this->assertEquals(
+			'',
+			$this->locator->getClassname(BASEPATH . 'bootstrap.php')
+		);
 	}
 
 }
diff --git a/tests/system/CLI/CommandRunnerTest.php b/tests/system/CLI/CommandRunnerTest.php
index 81102f2fa612..04bb83f7d1fc 100644
--- a/tests/system/CLI/CommandRunnerTest.php
+++ b/tests/system/CLI/CommandRunnerTest.php
@@ -90,7 +90,7 @@ public function testBadCommand()
 		stream_filter_remove($this->error_filter);
 
 		// make sure the result looks like a command list
-		$this->assertContains("Command 'bogus' not found", $result);
+		$this->assertContains('Command "bogus" not found', $result);
 	}
 
 }
diff --git a/tests/system/CodeIgniterTest.php b/tests/system/CodeIgniterTest.php
index b2eb0a6a1d64..6a04a0d089a1 100644
--- a/tests/system/CodeIgniterTest.php
+++ b/tests/system/CodeIgniterTest.php
@@ -3,7 +3,7 @@
 use Config\App;
 use Tests\Support\MockCodeIgniter;
 use CodeIgniter\Router\RouteCollection;
-use Tests\Support\Autoloader\MockFileLocator;
+use \CodeIgniter\Config\Services;
 
 /**
  * @backupGlobals enabled
@@ -135,7 +135,7 @@ public function testRun404OverrideByClosure()
 		$_SERVER['argc'] = 2;
 
 		// Inject mock router.
-		$routes = new RouteCollection(new MockFileLocator(new \Config\Autoload()), new \Config\Modules());
+		$routes = new RouteCollection(Services::locator(), new \Config\Modules());
 		$routes->setAutoRoute(false);
 		$routes->set404Override(function () {
 			echo '404 Override by Closure.';
diff --git a/tests/system/CommonFunctionsTest.php b/tests/system/CommonFunctionsTest.php
index e3705d82b406..287457bd96a1 100644
--- a/tests/system/CommonFunctionsTest.php
+++ b/tests/system/CommonFunctionsTest.php
@@ -3,14 +3,12 @@
 use CodeIgniter\Session\Handlers\FileHandler;
 use CodeIgniter\HTTP\Response;
 use Config\App;
-use Config\Autoload;
 use CodeIgniter\Config\Services;
 use CodeIgniter\Router\RouteCollection;
 use CodeIgniter\HTTP\RedirectResponse;
 use CodeIgniter\HTTP\URI;
 use CodeIgniter\HTTP\UserAgent;
 use Config\Logger;
-use Tests\Support\Autoloader\MockFileLocator;
 use Tests\Support\HTTP\MockIncomingRequest;
 use Tests\Support\Log\TestLogger;
 use Tests\Support\Session\MockSession;
@@ -102,7 +100,9 @@ public function testRedirectReturnsRedirectResponse()
 		$_SERVER['REQUEST_METHOD'] = 'GET';
 
 		$response = $this->createMock(\CodeIgniter\HTTP\Response::class);
-		$routes   = new \CodeIgniter\Router\RouteCollection(new \Tests\Support\Autoloader\MockFileLocator(new \Config\Autoload()), new \Config\Modules());
+		$routes   = new \CodeIgniter\Router\RouteCollection(
+			Services::locator(), new \Config\Modules()
+		);
 		\CodeIgniter\Services::injectMock('response', $response);
 		\CodeIgniter\Services::injectMock('routes', $routes);
 
@@ -267,7 +267,7 @@ public function testOldInput()
 		$this->config          = new App();
 		$this->config->baseURL = 'http://example.com';
 
-		$this->routes = new RouteCollection(new MockFileLocator(new Autoload()), new \Config\Modules());
+		$this->routes = new RouteCollection(Services::locator(), new \Config\Modules());
 		Services::injectMock('routes', $this->routes);
 
 		$this->request = new MockIncomingRequest($this->config, new URI('http://example.com'), null, new UserAgent());
@@ -303,7 +303,7 @@ public function testOldInputArray()
 		$this->config          = new App();
 		$this->config->baseURL = 'http://example.com';
 
-		$this->routes = new RouteCollection(new MockFileLocator(new Autoload()), new \Config\Modules());
+		$this->routes = new RouteCollection(Services::locator(), new \Config\Modules());
 		Services::injectMock('routes', $this->routes);
 
 		$this->request = new MockIncomingRequest($this->config, new URI('http://example.com'), null, new UserAgent());
diff --git a/tests/system/Config/ServicesTest.php b/tests/system/Config/ServicesTest.php
index f55bffffa254..e886a9eb7e24 100644
--- a/tests/system/Config/ServicesTest.php
+++ b/tests/system/Config/ServicesTest.php
@@ -22,6 +22,30 @@ public function tearDown()
 		$_SERVER = $this->original;
 	}
 
+	public function testNewAutoloader()
+	{
+		$actual = Services::autoloader();
+		$this->assertInstanceOf(\CodeIgniter\Autoloader\Autoloader::class, $actual);
+	}
+
+	public function testNewUnsharedAutoloader()
+	{
+		$actual = Services::autoloader(false);
+		$this->assertInstanceOf(\CodeIgniter\Autoloader\Autoloader::class, $actual);
+	}
+
+	public function testNewFileLocator()
+	{
+		$actual = Services::locator();
+		$this->assertInstanceOf(\CodeIgniter\Autoloader\FileLocator::class, $actual);
+	}
+
+	public function testNewUnsharedFileLocator()
+	{
+		$actual = Services::locator(false);
+		$this->assertInstanceOf(\CodeIgniter\Autoloader\FileLocator::class, $actual);
+	}
+
 	public function testNewCurlRequest()
 	{
 		$actual = Services::curlrequest();
@@ -81,6 +105,46 @@ public function testNewUnsharedClirequest()
 		$this->assertInstanceOf(\CodeIgniter\HTTP\CLIRequest::class, $actual);
 	}
 
+	public function testNewEmail()
+	{
+		$actual = Services::email();
+		$this->assertInstanceOf(\CodeIgniter\Email\Email::class, $actual);
+
+		$actual->fromName = 'Zoboomafoo';
+		$this->assertEquals('Zoboomafoo', Services::email()->fromName);
+		$this->assertEquals('Zoboomafoo', Services::email(new \Config\Email())->fromName);
+	}
+
+	public function testNewUnsharedEmail()
+	{
+		$actual = Services::email(null, false);
+		$this->assertInstanceOf(\CodeIgniter\Email\Email::class, $actual);
+
+		$actual->fromName = 'Zoboomafoo';
+		$this->assertEquals('', Services::email(null, false)->fromName);
+		$this->assertEquals('', Services::email(new \Config\Email(), false)->fromName);
+	}
+
+	public function testNewLanguage()
+	{
+		$actual = Services::language();
+		$this->assertInstanceOf(\CodeIgniter\Language\Language::class, $actual);
+		$this->assertEquals('en', $actual->getLocale());
+
+		Services::language('la');
+		$this->assertEquals('la', $actual->getLocale());
+	}
+
+	public function testNewUnsharedLanguage()
+	{
+		$actual = Services::language(null, false);
+		$this->assertInstanceOf(\CodeIgniter\Language\Language::class, $actual);
+		$this->assertEquals('en', $actual->getLocale());
+
+		Services::language('la', false);
+		$this->assertEquals('en', $actual->getLocale());
+	}
+
 	public function testNewPager()
 	{
 		$actual = Services::pager(null);
diff --git a/tests/system/HTTP/RedirectResponseTest.php b/tests/system/HTTP/RedirectResponseTest.php
index a9d24d621066..e913db325279 100644
--- a/tests/system/HTTP/RedirectResponseTest.php
+++ b/tests/system/HTTP/RedirectResponseTest.php
@@ -3,11 +3,9 @@
 namespace CodeIgniter\HTTP;
 
 use Config\App;
-use Config\Autoload;
 use CodeIgniter\Config\Services;
 use CodeIgniter\Validation\Validation;
 use CodeIgniter\Router\RouteCollection;
-use Tests\Support\Autoloader\MockFileLocator;
 use Tests\Support\HTTP\MockIncomingRequest;
 
 class RedirectResponseTest extends \CIUnitTestCase
@@ -29,7 +27,7 @@ public function setUp()
 		$this->config          = new App();
 		$this->config->baseURL = 'http://example.com';
 
-		$this->routes = new RouteCollection(new MockFileLocator(new Autoload()), new \Config\Modules());
+		$this->routes = new RouteCollection(Services::locator(), new \Config\Modules());
 		Services::injectMock('routes', $this->routes);
 
 		$this->request = new MockIncomingRequest($this->config, new URI('http://example.com'), null, new UserAgent());
diff --git a/tests/system/Router/RouteCollectionTest.php b/tests/system/Router/RouteCollectionTest.php
index 009d2f17404a..8cafb3f25e73 100644
--- a/tests/system/Router/RouteCollectionTest.php
+++ b/tests/system/Router/RouteCollectionTest.php
@@ -1,7 +1,7 @@
 <?php
 namespace CodeIgniter\Router;
 
-use Tests\Support\Autoloader\MockFileLocator;
+use CodeIgniter\Config\Services;
 use CodeIgniter\Router\Exceptions\RouterException;
 
 /**
@@ -24,11 +24,9 @@ protected function getCollector(array $config = [], array $files = [], $moduleCo
 		];
 		$config   = array_merge($config, $defaults);
 
-		$autoload       = new \Config\Autoload();
-		$autoload->psr4 = $config;
+		Services::autoloader()->addNamespace($config);
 
-		$loader = new MockFileLocator($autoload);
-		$loader->setFiles($files);
+		$loader = Services::locator();
 
 		if ($moduleConfig === null)
 		{
diff --git a/tests/system/Router/RouterTest.php b/tests/system/Router/RouterTest.php
index 61bf929b0cd3..57706ed5f7c4 100644
--- a/tests/system/Router/RouterTest.php
+++ b/tests/system/Router/RouterTest.php
@@ -1,7 +1,7 @@
 <?php
 namespace CodeIgniter\Router;
 
-use Tests\Support\Autoloader\MockFileLocator;
+use CodeIgniter\Config\Services;
 
 class RouterTest extends \CIUnitTestCase
 {
@@ -24,7 +24,7 @@ public function setUp()
 
 		$moduleConfig          = new \Config\Modules;
 		$moduleConfig->enabled = false;
-		$this->collection      = new RouteCollection(new MockFileLocator(new \Config\Autoload()), $moduleConfig);
+		$this->collection      = new RouteCollection(Services::locator(), $moduleConfig);
 
 		$routes = [
 			'users'                                           => 'Users::index',
diff --git a/tests/system/Validation/ValidationTest.php b/tests/system/Validation/ValidationTest.php
index 986f88c77eae..b355f637dc41 100644
--- a/tests/system/Validation/ValidationTest.php
+++ b/tests/system/Validation/ValidationTest.php
@@ -43,7 +43,7 @@ public function setUp()
 	{
 		parent::setUp();
 
-		Services::reset();
+		Services::reset(true);
 
 		$this->validation = new Validation((object) $this->config, \Config\Services::renderer());
 		$this->validation->reset();
diff --git a/tests/system/View/ParserFilterTest.php b/tests/system/View/ParserFilterTest.php
index 5a186d2be5a0..a93334ff76ce 100644
--- a/tests/system/View/ParserFilterTest.php
+++ b/tests/system/View/ParserFilterTest.php
@@ -12,7 +12,8 @@ public function setUp()
 	{
 		parent::setUp();
 
-		$this->loader   = new \CodeIgniter\Autoloader\FileLocator(new \Config\Autoload());
+		$this->loader = \CodeIgniter\Config\Services::locator();
+		;
 		$this->viewsDir = __DIR__ . '/Views';
 		$this->config   = new Config\View();
 	}
diff --git a/tests/system/View/ParserPluginTest.php b/tests/system/View/ParserPluginTest.php
index a656e4c15f2f..4b3df74aabe4 100644
--- a/tests/system/View/ParserPluginTest.php
+++ b/tests/system/View/ParserPluginTest.php
@@ -1,17 +1,22 @@
 <?php
 
-use CodeIgniter\View\Parser;
-
 class ParserPluginTest extends \CIUnitTestCase
 {
+	/**
+	 * @var \CodeIgniter\View\Parser
+	 */
 	protected $parser;
+	/**
+	 * @var \CodeIgniter\Validation\Validation
+	 */
 	protected $validator;
 
 	public function setUp()
 	{
 		parent::setUp();
 
-		\Config\Services::reset();
+		\Config\Services::reset(true);
+
 		$this->parser    = \Config\Services::parser();
 		$this->validator = \Config\Services::validation();
 	}
diff --git a/tests/system/View/ParserTest.php b/tests/system/View/ParserTest.php
index 671168566bfc..5647ea37a688 100644
--- a/tests/system/View/ParserTest.php
+++ b/tests/system/View/ParserTest.php
@@ -10,7 +10,7 @@ public function setUp()
 	{
 		parent::setUp();
 
-		$this->loader   = new \CodeIgniter\Autoloader\FileLocator(new \Config\Autoload());
+		$this->loader   = \CodeIgniter\Config\Services::locator();
 		$this->viewsDir = __DIR__ . '/Views';
 		$this->config   = new Config\View();
 	}
diff --git a/tests/system/View/ViewTest.php b/tests/system/View/ViewTest.php
index a322d9f826c0..2e64bf553feb 100644
--- a/tests/system/View/ViewTest.php
+++ b/tests/system/View/ViewTest.php
@@ -15,7 +15,7 @@ public function setUp()
 	{
 		parent::setUp();
 
-		$this->loader   = new \CodeIgniter\Autoloader\FileLocator(new \Config\Autoload());
+		$this->loader   = \CodeIgniter\Config\Services::locator();
 		$this->viewsDir = __DIR__ . '/Views';
 		$this->config   = new Config\View();
 	}