diff --git a/Procfile b/Procfile
new file mode 100644
index 0000000..7f7ea18
--- /dev/null
+++ b/Procfile
@@ -0,0 +1,2 @@
+repl: fennel
+test: find . | entr sh test/run.sh
\ No newline at end of file
diff --git a/doc/index.html b/doc/index.html
index df733e6..06ddcea 100644
--- a/doc/index.html
+++ b/doc/index.html
@@ -17,10 +17,20 @@
   </body>
 
 
-  <h2>Features</h2>
-
   Dunlin is a GTK-based Webkit browser which can be extended in
   (indeed, is mostly written in) Fennel.
 
+  <h2>Hacking</h2>
+
+  <pre>
+    $ nix-shell
+    nix-shell$ overmind start -D
+    nix-shell$ overmind connect
+  </pre>
+
+  This starts a fennel interpreter and a test runner in tmux windows.
+  Use <pre>C-b n</pre> to switch between them or <pre>C-b d</pre>
+  to detach.
+
 
 </html>
diff --git a/shell.nix b/shell.nix
index 22fc4b9..cb68fc2 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,6 +1,10 @@
 with import <nixpkgs> {} ;
 let just = callPackage ./. {};
 in just.overrideAttrs(o: {
-  nativeBuildInputs = o.nativeBuildInputs ++ [ pkgs.socat ];
+  nativeBuildInputs = o.nativeBuildInputs ++ (with pkgs; [
+    socat
+    overmind
+    entr
+  ]);
   JUST_HACKING = 1;
 })
diff --git a/test/run.sh b/test/run.sh
new file mode 100644
index 0000000..d774a4c
--- /dev/null
+++ b/test/run.sh
@@ -0,0 +1,4 @@
+#!/usr/bin/env sh
+for i in test/*.fnl; do
+    fennel --correlate $i && echo $i OK
+done