diff --git a/tests/includes/mock-fs.php b/tests/includes/mock-fs.php
new file mode 100644
index 0000000000..3a99f8ba97
--- /dev/null
+++ b/tests/includes/mock-fs.php
@@ -0,0 +1,226 @@
+<?php
+class WP_Filesystem_MockFS extends WP_Filesystem_Base {
+	private $cwd;
+
+	// Holds a array of objects which contain an array of objects, etc.
+	private $fs = null;
+
+	// Holds a array of /path/to/file.php and /path/to/dir/ map to an object in $fs above
+	// a fast more efficient way of determining if a path exists, and access to that node
+	private $fs_map = array();
+
+	public $verbose = false; // Enable to debug WP_Filesystem_Base::find_folder() / etc.
+	public $errors = array();
+	public $method = 'MockFS';
+
+	function __construct() {}
+
+	function connect() {
+		return true;
+	}
+
+	// Copy of core's function, but accepts a path.
+	function abspath( $path = false ) {
+		if ( ! $path )
+			$path = ABSPATH;
+		$folder = $this->find_folder( $path );
+
+		// Perhaps the FTP folder is rooted at the WordPress install, Check for wp-includes folder in root, Could have some false positives, but rare.
+		if ( ! $folder && $this->is_dir('/wp-includes') )
+			$folder = '/';
+		return $folder;
+	}
+
+	// Mock FS specific functions:
+
+	/**
+	 * Sets initial filesystem environment and/or clears the current environment.
+	 * Can also be passed the initial filesystem to be setup which is passed to self::setfs()
+	 */
+	function init( $paths = '', $home_dir = '/' ) {
+		$this->fs = new MockFS_Directory_Node( '/' );
+		$this->fs_map = array(
+			'/' => $this->fs,
+		);
+		$this->cache = array(); // Used by find_folder() and friends
+		$this->cwd = isset( $this->fs_map[ $home_dir ] ) ? $this->fs_map[ $home_dir ] : '/';
+		$this->setfs( $paths );
+	}
+
+	/**
+	 * "Bulk Loads" a filesystem into the internal virtual filesystem
+	 */
+	function setfs( $paths ) {
+		if ( ! is_array($paths) )
+			$paths = explode( "\n", $paths );
+
+		$paths = array_filter( array_map( 'trim', $paths ) );
+
+		foreach ( $paths as $path ) {
+			// Allow for comments
+			if ( '#' == $path[0] )
+				continue;
+
+			// Directories
+			if ( '/' == $path[ strlen($path) -1 ] )
+				$this->mkdir( $path );
+			else // Files (with dummy content for now)
+				$this->put_contents( $path, 'This is a test file' );
+		}
+
+	}
+
+	/**
+	 * Locates a filesystem "node"
+	 */
+	private function locate_node( $path ) {
+		return isset( $this->fs_map[ $path ] ) ? $this->fs_map[ $path ] : false;
+	}
+
+	/**
+	 * Locates a filesystem node for the parent of the given item
+	 */
+	private function locate_parent_node( $path ) {
+		return $this->locate_node( trailingslashit( dirname( $path ) ) );
+	}
+
+	// Here starteth the WP_Filesystem functions.
+
+	function mkdir( $path, /* Optional args are ignored */ $chmod = false, $chown = false, $chgrp = false ) {
+		$path = trailingslashit( $path );
+
+		$parent_node = $this->locate_parent_node( $path );
+		if ( ! $parent_node ) {
+			$this->mkdir( dirname( $path ) );
+			$parent_node = $this->locate_parent_node( $path );
+			if ( ! $parent_node )
+				return false;
+		}
+
+		$node = new MockFS_Directory_Node( $path );
+
+		$parent_node->children[ $node->name ] = $node;
+		$this->fs_map[ $path ] = $node;
+
+		return true;
+	}
+
+	function put_contents( $path, $contents = '', $mode = null ) {
+		if ( ! $this->is_dir( dirname( $path ) ) )
+			$this->mkdir( dirname( $path ) );
+
+		$parent = $this->locate_parent_node( $path );
+		$new_file = new MockFS_File_Node( $path, $contents );
+
+		$parent->children[ $new_file->name ] = $new_file;
+		$this->fs_map[ $path ] = $new_file;
+	}
+
+	function get_contents( $file ) {
+		if ( ! $this->is_file( $file ) )
+			return false;
+		return $this->fs_map[ $file ]->contents;
+	}
+
+	function cwd() {
+		return $this->cwd->path;
+	}
+
+	function chdir( $path ) {
+		if ( ! isset( $this->fs_map[ $path ] ) )
+			return false;
+
+		$this->cwd = $this->fs_map[ $path ];
+		return true;
+	}
+
+	function exists( $path ) {
+		return isset( $this->fs_map[ $path ] ) || isset( $this->fs_map[ trailingslashit( $path ) ] );
+	}
+
+	function is_file( $file ) {
+		return isset( $this->fs_map[ $file ] ) && $this->fs_map[ $file ]->is_file();
+	}
+
+	function is_dir( $path ) {
+		$path = trailingslashit( $path );
+
+		return isset( $this->fs_map[ $path ] ) && $this->fs_map[ $path ]->is_dir();
+	}
+
+	function dirlist( $path = '.', $include_hidden = true, $recursive = false ) {
+
+		if ( empty( $path ) || '.' == $path )
+			$path = $this->cwd();
+
+		if ( ! $this->exists( $path ) )
+			return false;
+
+		$limit_file = false;
+		if ( $this->is_file( $path ) ) {
+			$limit_file = $this->locate_node( $path )->name;
+			$path = dirname( $path ) . '/';
+		}
+
+		$ret = array();
+		foreach ( $this->fs_map[ $path ]->children as $entry ) {
+			if ( '.' == $entry->name || '..' == $entry->name )
+				continue;
+
+			if ( ! $include_hidden && '.' == $entry->name )
+				continue;
+
+			if ( $limit_file && $entry->name != $limit_file )
+				continue;
+
+			$struc = array();
+			$struc['name'] = $entry->name;
+			$struc['type'] = $entry->type;
+
+			if ( 'd' == $struc['type'] ) {
+				if ( $recursive )
+					$struc['files'] = $this->dirlist( trailingslashit( $path ) . trailingslashit( $struc['name'] ), $include_hidden, $recursive );
+				else
+					$struc['files'] = array();
+			}
+
+			$ret[ $entry->name ] = $struc;
+		}
+		return $ret;
+	}
+
+}
+
+class MockFS_Node {
+	public $name; // The "name" of the entry, does not include a slash (exception, root)
+	public $type; // The type of the entry 'f' for file, 'd' for Directory
+	public $path; // The full path to the entry.
+
+	function __construct( $path ) {
+		$this->path = $path;
+		$this->name = basename( $path );
+	}
+
+	function is_file() {
+		return $this->type == 'f';
+	}
+
+	function is_dir() {
+		return $this->type == 'd';
+	}
+}
+
+class MockFS_Directory_Node extends MockFS_Node {
+	public $type = 'd';
+	public $children = array(); // The child nodes of this directory
+}
+
+class MockFS_File_Node extends MockFS_Node {
+	public $type = 'f';
+	public $contents = ''; // The contents of the file
+
+	function __construct( $path, $contents = '' ) {
+		parent::__construct( $path );
+		$this->contents = $contents;
+	}
+}
\ No newline at end of file
diff --git a/tests/tests/filesystem/base.php b/tests/tests/filesystem/base.php
new file mode 100644
index 0000000000..f13b46a10f
--- /dev/null
+++ b/tests/tests/filesystem/base.php
@@ -0,0 +1,43 @@
+<?php
+
+/**
+ * This class is designed to make use of MockFS, a Virtual in-memory filesystem compatible with WP_Filesystem
+ */
+abstract class WP_Filesystem_UnitTestCase extends WP_UnitTestCase {
+	function setUp() {
+		add_filter( 'filesystem_method_file', array( $this, 'filter_abstraction_file' ) );
+		add_filter( 'filesystem_method', array( $this, 'filter_fs_method' ) );
+		WP_Filesystem();
+	}
+
+	function tearDown() {
+		global $wp_filesystem;
+		remove_filter( 'filesystem_method_file', array( $this, 'filter_abstraction_file' ) );
+		remove_filter( 'filesystem_method', array( $this, 'filter_fs_method' ) );
+		unset( $wp_filesystem );
+
+		parent::tearDown();
+	}
+
+	function filter_fs_method( $method ) {
+		return 'MockFS';
+	}
+	function filter_abstraction_file( $file ) {
+		return dirname( dirname( dirname( __FILE__ ) ) ) . '/includes/mock-fs.php';
+	}
+
+	function test_is_MockFS_sane() {
+		global $wp_filesystem;
+		$this->assertTrue( is_a( $wp_filesystem, 'WP_Filesystem_MockFS' ) );
+
+		$wp_filesystem->init('/');
+
+		// Test creation/exists checks
+		$this->assertFalse( $wp_filesystem->is_dir( '/test/' ) );
+		$wp_filesystem->mkdir( '/test' );
+		$this->assertTrue( $wp_filesystem->exists( '/test' ) );
+		$this->assertTrue( $wp_filesystem->is_dir( '/test/' ) );
+		$this->assertFalse( $wp_filesystem->is_file( '/test' ) );
+		//$this->assertFalse( true );
+	}
+}
\ No newline at end of file
diff --git a/tests/tests/filesystem/find_folder.php b/tests/tests/filesystem/find_folder.php
new file mode 100644
index 0000000000..b623ac664b
--- /dev/null
+++ b/tests/tests/filesystem/find_folder.php
@@ -0,0 +1,107 @@
+<?php
+
+/**
+ * @group filesystem
+ * @group wp-filesystem
+ */
+class WP_Filesystem_find_folder_UnitTestCases extends WP_Filesystem_UnitTestCase {
+
+	function test_ftp_has_root_access() {
+		global $wp_filesystem;
+		$fs = $wp_filesystem;
+		$fs->init('
+			/var/www/wordpress/
+			/var/www/wordpress/wp-includes/
+			/var/www/wordpress/index.php
+		');
+
+		$path = $fs->find_folder( '/var/www/wordpress/' );
+		$this->assertEquals( '/var/www/wordpress/', $path );
+
+		$path = $fs->find_folder( '/this/directory/doesnt/exist/' );
+		$this->assertFalse( $path );
+
+	}
+
+	function test_sibling_wordpress_in_subdir() {
+		global $wp_filesystem;
+		$fs = $wp_filesystem;
+		$fs->init('
+			/www/example.com/wordpress/
+			/www/example.com/wordpress/wp-includes/
+			/www/example.com/wordpress/index.php
+			/www/wp.example.com/wordpress/
+			/www/wp.example.com/wordpress/wp-includes/
+			/www/wp.example.com/wordpress/wp-content/
+			/www/wp.example.com/wordpress/index.php
+			/www/index.php
+		');
+
+		$path = $fs->find_folder( '/var/www/example.com/wordpress/' );
+		$this->assertEquals( '/www/example.com/wordpress/', $path );
+		
+		$path = $fs->find_folder( '/var/www/wp.example.com/wordpress/wp-content/' );
+		$this->assertEquals( '/www/wp.example.com/wordpress/wp-content/', $path );
+
+	}
+
+	/**
+	 * Two WordPress installs, with one contained within the other
+	 * FTP / = /var/www/example.com/ on Disk
+	 * example.com at /
+	 * wp.example.com at /wp.example.com/wordpress/
+	 */
+	function test_subdir_of_another() {
+		global $wp_filesystem;
+		$fs = $wp_filesystem;
+		$fs->init('
+			/wp.example.com/index.php
+			/wp.example.com/wordpress/
+			/wp.example.com/wordpress/wp-includes/
+			/wp.example.com/wordpress/index.php
+			/wp-includes/
+			/index.php
+		');
+
+		$path = $fs->abspath( '/var/www/example.com/wp.example.com/wordpress/' );
+		$this->assertEquals( '/wp.example.com/wordpress/', $path );
+		
+		$path = $fs->abspath( '/var/www/example.com/' );
+		$this->assertEquals( '/', $path );
+
+	}
+
+	/**
+	 * Test the WordPress ABSPATH containing TWO tokens (www) of which exists in the current FTP home.
+	 *
+	 * @ticket 20934
+	 */
+	function test_multiple_tokens_in_path1() {
+		global $wp_filesystem;
+		$fs = $wp_filesystem;
+		$fs->init('
+			# www.example.com
+			/example.com/www/index.php
+			/example.com/www/wp-includes/
+			/example.com/www/wp-content/plugins/
+			
+			# sub.example.com
+			/example.com/sub/index.php
+			/example.com/sub/wp-includes/
+			/example.com/sub/wp-content/plugins/
+		');
+
+		// www.example.com
+		$path = $fs->abspath( '/var/www/example.com/www/' );
+		$this->assertEquals( '/example.com/www/', $path );
+
+		// sub.example.com
+		$path = $fs->abspath( '/var/www/example.com/sub/' );
+		$this->assertEquals( '/example.com/sub/', $path );
+
+		// sub.example.com - Plugins
+		$path = $fs->find_folder( '/var/www/example.com/sub/wp-content/plugins/' );
+		$this->assertEquals( '/example.com/sub/wp-content/plugins/', $path );
+	}
+
+}
\ No newline at end of file