diff --git a/src/Ko/ProcessManager.php b/src/Ko/ProcessManager.php
index de6e1cd..c321aba 100644
--- a/src/Ko/ProcessManager.php
+++ b/src/Ko/ProcessManager.php
@@ -70,23 +70,29 @@ class ProcessManager implements \Countable
      */
     protected $signalHandler;
 
-    public function __construct()
+    public function __construct(SignalHandler $signalHandler = null)
     {
         $this->children = [];
         $this->spawnWatch = [];
         $this->sigTerm = false;
 
+        if (isset($signalHandler)) {
+            $this->signalHandler = $signalHandler;
+
+        } else {
+            $this->signalHandler = new SignalHandler();
+        }
+
         $this->setupSignalHandlers();
     }
 
     protected function setupSignalHandlers()
     {
-        $this->signalHandler = new SignalHandler();
-        $this->signalHandler->registerHandler(SIGCHLD, function() {
+        $this->signalHandler->registerHandler(SIGCHLD, function () {
             $this->handleSigChild();
         });
 
-        $this->signalHandler->registerHandler(SIGTERM, function() {
+        $this->signalHandler->registerHandler(SIGTERM, function () {
             $this->handleSigTerm();
         });
     }
@@ -114,7 +120,7 @@ public function handleSigTerm()
         foreach ($this->children as $process) {
             $process->kill();
         }
-        
+
         $this->internalEmit('shutdown');
     }
 
@@ -310,3 +316,4 @@ public function dispatch()
         return $this;
     }
 }
+