diff --git a/PHPCI/Helper/CommandExecutorInterface.php b/PHPCI/Helper/CommandExecutorInterface.php
new file mode 100644
index 00000000..8e75b166
--- /dev/null
+++ b/PHPCI/Helper/CommandExecutorInterface.php
@@ -0,0 +1,35 @@
+<?php
+
+namespace PHPCI\Helper;
+
+use \PHPCI\Logging\BuildLogger;
+
+interface CommandExecutorInterface
+{
+    /**
+     * @param BuildLogger $logger
+     * @param string      $rootDir
+     * @param bool        $quiet
+     * @param bool        $verbose
+     */
+    public function __construct(BuildLogger $logger, $rootDir, &$quiet = false, &$verbose = false);
+
+    /**
+     * Executes shell commands. Accepts multiple arguments the first
+     * is the template and everything else is inserted in. c.f. sprintf
+     * @return bool Indicates success
+     */
+    public function executeCommand();
+
+    /**
+     * Returns the output from the last command run.
+     */
+    public function getLastOutput();
+
+    /**
+     * Find a binary required by a plugin.
+     * @param string $binary
+     * @return null|string
+     */
+    public function findBinary($binary);
+}