diff --git a/src/IDF/Scm/Monotone.php b/src/IDF/Scm/Monotone.php
index 5ec5bfa..7a3c210 100644
--- a/src/IDF/Scm/Monotone.php
+++ b/src/IDF/Scm/Monotone.php
@@ -36,12 +36,12 @@ class IDF_Scm_Monotone extends IDF_Scm
     private static $instances = array();
 
     /**
-     * @see IDF_Scm::__construct()
+     * Constructor
      */
-    public function __construct($project)
+    public function __construct(IDF_Project $project, IDF_Scm_Monotone_IStdio $stdio)
     {
         $this->project = $project;
-        $this->stdio = new IDF_Scm_Monotone_Stdio($project);
+        $this->stdio = $stdio;
     }
 
     /**
@@ -458,8 +458,9 @@ class IDF_Scm_Monotone extends IDF_Scm
     public static function factory($project)
     {
         if (!array_key_exists($project->shortname, self::$instances)) {
+            $stdio = new IDF_Scm_Monotone_Stdio($project);
             self::$instances[$project->shortname] =
-                new IDF_Scm_Monotone($project);
+                new IDF_Scm_Monotone($project, $stdio);
         }
         return self::$instances[$project->shortname];
     }
@@ -676,8 +677,8 @@ class IDF_Scm_Monotone extends IDF_Scm
 
         $parents = $this->stdio->exec(array('parents', $revs[0]));
         $res['parents'] = preg_split("/\n/", $parents, -1, PREG_SPLIT_NO_EMPTY);
-        
-        $certs = $this->_getCerts($revs[0]);        
+
+        $certs = $this->_getCerts($revs[0]);
         // FIXME: this assumes that author, date and changelog are always given
         $res['author'] = implode(', ', $certs['author']);
 
diff --git a/src/IDF/Scm/Monotone/IStdio.php b/src/IDF/Scm/Monotone/IStdio.php
new file mode 100644
index 0000000..b6cf544
--- /dev/null
+++ b/src/IDF/Scm/Monotone/IStdio.php
@@ -0,0 +1,66 @@
+<?php
+/* -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+# ***** BEGIN LICENSE BLOCK *****
+# This file is part of InDefero, an open source project management application.
+# Copyright (C) 2011 Céondo Ltd and contributors.
+#
+# InDefero is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# InDefero is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#
+# ***** END LICENSE BLOCK ***** */
+
+/**
+ * Monotone stdio interface
+ *
+ * @author Thomas Keller <me@thomaskeller.biz>
+ */
+interface IDF_Scm_Monotone_IStdio
+{
+    /**
+     * Constructor
+     */
+    public function __construct(IDF_Project $project);
+
+    /**
+     * Starts the stdio process and resets the command counter
+     */
+    public function start();
+
+    /**
+     * Stops the stdio process and closes all pipes
+     */
+    public function stop();
+
+    /**
+     * Executes a command over stdio and returns its result
+     *
+     * @param array Array of arguments
+     * @param array Array of options as key-value pairs. Multiple options
+     *              can be defined in sub-arrays, like
+     *              "r" => array("123...", "456...")
+     * @return string
+     */
+    public function exec(array $args, array $options = array());
+
+    /**
+     * Returns the last out-of-band output for a previously executed
+     * command as associative array with 'e' (error), 'w' (warning),
+     * 'p' (progress) and 't' (ticker, unparsed) as keys
+     *
+     * @return array
+     */
+    public function getLastOutOfBandOutput();
+}
+
diff --git a/src/IDF/Scm/Monotone/Stdio.php b/src/IDF/Scm/Monotone/Stdio.php
index 86c4b50..c47e005 100644
--- a/src/IDF/Scm/Monotone/Stdio.php
+++ b/src/IDF/Scm/Monotone/Stdio.php
@@ -21,6 +21,8 @@
 #
 # ***** END LICENSE BLOCK ***** */
 
+require_once 'IDF/Scm/Monotone/IStdio.php';
+
 /**
  * Monotone stdio class
  *
@@ -29,7 +31,7 @@
  *
  * @author Thomas Keller <me@thomaskeller.biz>
  */
-class IDF_Scm_Monotone_Stdio
+class IDF_Scm_Monotone_Stdio implements IDF_Scm_Monotone_IStdio
 {
     /** this is the most recent STDIO version. The number is output
         at the protocol start. Older versions of monotone (prior 0.47)
@@ -68,7 +70,7 @@ class IDF_Scm_Monotone_Stdio
      *
      * @return string
      */
-    public function _getAuthOptions()
+    private function _getAuthOptions()
     {
         $prjconf = $this->project->getConf();
         $name = $prjconf->getVal('mtn_client_key_name', false);
diff --git a/src/IDF/Scm/Monotone/ZipRender.php b/src/IDF/Scm/Monotone/ZipRender.php
index 41f9f7d..eddc4fc 100644
--- a/src/IDF/Scm/Monotone/ZipRender.php
+++ b/src/IDF/Scm/Monotone/ZipRender.php
@@ -24,7 +24,7 @@
 require_once(IDF_PATH.'/../contrib/zipstream-php-0.2.2/zipstream.php');
 
 /**
- * Special response object to output 
+ * Special response object to output
  *
  * The Content-Length will not be set as it is not possible to predict it.
  *
@@ -45,7 +45,7 @@ class IDF_Scm_Monotone_ZipRender extends Pluf_HTTP_Response
     private $stdio = null;
     private $revision = null;
 
-    function __construct($stdio, $revision)
+    function __construct(IDF_Scm_Monotone_IStdio $stdio, $revision)
     {
         parent::__construct($revision, 'application/x-zip');
         $this->stdio = $stdio;