diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..41fbeb0
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+**/result
diff --git a/nix/default.nix b/nix/default.nix
new file mode 100644
index 0000000..12f1291
--- /dev/null
+++ b/nix/default.nix
@@ -0,0 +1,11 @@
+{ nixpkgs ? ./nixpkgs }:
+import (import nixpkgs) {
+  config = { allowUnfree = true; };
+  overlays = [
+    (self: super: { snack-lib = import ../snack;} )
+    (self: super: { snack = self.writeScriptBin "snack"
+      ''
+        ${self.nix}/bin/nix-build snack.nix
+      ''; })
+  ];
+}
diff --git a/nix/nixpkgs/default.nix b/nix/nixpkgs/default.nix
new file mode 100644
index 0000000..992b009
--- /dev/null
+++ b/nix/nixpkgs/default.nix
@@ -0,0 +1,6 @@
+let
+  spec = builtins.fromJSON (builtins.readFile ./nixpkgs-src.json);
+  rev = spec.rev;
+  url = "https://github.com/${spec.owner}/${spec.repo}/archive/${spec.rev}.tar.gz";
+in
+  builtins.fetchTarball url
diff --git a/nix/src.json b/nix/nixpkgs/nixpkgs-src.json
similarity index 100%
rename from nix/src.json
rename to nix/nixpkgs/nixpkgs-src.json
diff --git a/nix/update b/nix/update
index 5ba0682..abe6370 100755
--- a/nix/update
+++ b/nix/update
@@ -5,8 +5,6 @@
 # See https://gist.github.com/zimbatm/de5350245874361762b6a4dfe5366530
 set -euo pipefail
 
-cd "$(dirname "$0")" || exit 1
-
 branch=master
 
 owner=NixOS
@@ -16,7 +14,7 @@ url=https://github.com/$owner/$repo/archive/$rev.tar.gz
 
 release_sha256=$(nix-prefetch-url --unpack "$url")
 
-cat <<NIXPKGS | tee src.json
+cat <<NIXPKGS | tee nix/nixpkgs/nixpkgs-src.json
 {
   "owner": "$owner",
   "repo": "$repo",
diff --git a/script/test b/script/test
new file mode 100755
index 0000000..81e8b8b
--- /dev/null
+++ b/script/test
@@ -0,0 +1,16 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i bash
+#!nix-shell -I nixpkgs=./nix
+#!nix-shell -p snack
+#!nix-shell --pure
+# vim: ft=sh sw=2 et
+
+set -eux
+
+pushd tests/flat
+snack build
+popd
+
+pushd tests/nested
+snack build
+popd
diff --git a/default.nix b/snack/default.nix
similarity index 74%
rename from default.nix
rename to snack/default.nix
index 2d07ea2..8ab2355 100644
--- a/default.nix
+++ b/snack/default.nix
@@ -1,8 +1,7 @@
+# TODO: currently single out derivations append the PWD
 let
   # Use pinned packages
-  _nixpkgs = import <nixpkgs> {};
-  nixpkgs = _nixpkgs.fetchFromGitHub (_nixpkgs.lib.importJSON ./nix/src.json);
-  pkgs = import nixpkgs {config={}; overlays=[];};
+  pkgs = import (../nix) {};
 
   # Takes a (string) filepath and creates a derivation for that file (and for
   # that file only)
@@ -13,17 +12,26 @@ let
           topLevel = (builtins.toString base) + "/";
           actual = (pkgs.lib.strings.removePrefix topLevel path);
           expected = file;
-      in expected == actual;
+      in
+        (expected == actual) ||
+        (type == "directory" && (pkgs.lib.strings.hasPrefix actual expected));
+      mod = fileToModule file;
 
     in pkgs.stdenv.mkDerivation {
-      name = file;
+      name = mod;
       src = builtins.filterSource (pred file) base;
-      builder = pkgs.writeScript (file + "-builder")
+      builder = pkgs.writeScript (mod + "-builder")
       # TODO: make sure the file actually exists and that there's only one
       ''
+        echo "Singling out module ${mod} (file is ${file})"
         source $stdenv/setup
         mkdir -p $out
-        cp -a $src/* $out/
+        echo "Running: cp $src/${file} $out/${file}"
+        echo "Listing $src"
+        ls $src/**/*
+        mkdir -p $(dirname $out/${file})
+        cp $src/${file} $out/${file}
+        echo "Done: Singling out module ${mod} (file is ${file})"
       '';
     };
 
@@ -36,6 +44,13 @@ let
   moduleToFile = mod:
     (pkgs.lib.strings.replaceChars ["."] ["/"] mod) + ".hs";
 
+  moduleToObject = mod:
+    (pkgs.lib.strings.replaceChars ["."] ["/"] mod) + ".o";
+
+  fileToModule = file:
+    pkgs.lib.strings.removeSuffix ".hs"
+      (pkgs.lib.strings.replaceChars ["/"] ["."] file);
+
   singleOutModule = base: mod: singleOut base (moduleToFile mod);
 
   buildModule = base: mod:
@@ -66,7 +81,7 @@ let
         echo "Compiling module ${mod.moduleName}"
         # Set a tmpdir we have control over, otherwise GHC fails, not sure why
         mkdir -p tmp
-        ghc -tmpdir tmp/ ${mod.moduleName}.hs -c \
+        ghc -tmpdir tmp/ ${moduleToFile mod.moduleName} -c \
           -outputdir $out \
           2>&1
         echo "Done building module ${mod.moduleName}"
@@ -84,16 +99,17 @@ let
       go = mod: attrs0:
         let
           objectName = x:
+            # TODO: can't use "moduleName.o" because some modules get
+            # renamed to "Main.o" :/
+            # Also, hard coding the object file based on the module name feels
+            # icky
             if x.moduleIsMain
             then "Main.o"
-            else x.moduleName + ".o";
+            else moduleToObject x.moduleName;
           attrs1 = f attrs0 mod;
           f = acc: elem:
             if pkgs.lib.attrsets.hasAttr elem.moduleName acc
             then acc
-            # TODO: module path instead of module name
-            # TODO: can't use "moduleName.o" because some modules get
-            # renamed to "Main.o"
             else acc //
               { "${elem.moduleName}" =
                 "${buildModule base elem}/${objectName elem}";
@@ -120,8 +136,8 @@ let
           ];
       };
 
-  # TODO: use ghc -M for module dependencies
-  modB = makeModuleSpec "B" [] false;
-  modA = makeModuleSpec "A" [modB] true;
-
-in linkModuleObjects ./. modA
+  ## TODO: use ghc -M for module dependencies
+in
+  {
+    inherit linkModuleObjects makeModuleSpec;
+  }
diff --git a/A.hs b/tests/flat/A.hs
similarity index 100%
rename from A.hs
rename to tests/flat/A.hs
diff --git a/B.hs b/tests/flat/B.hs
similarity index 100%
rename from B.hs
rename to tests/flat/B.hs
diff --git a/tests/flat/README.md b/tests/flat/README.md
new file mode 100644
index 0000000..077a01e
--- /dev/null
+++ b/tests/flat/README.md
@@ -0,0 +1,3 @@
+# Flat
+
+Makes sure that two modules, `A.hs` and `B.hs`, can be built into an executable
diff --git a/tests/flat/snack.nix b/tests/flat/snack.nix
new file mode 100644
index 0000000..9d45ae8
--- /dev/null
+++ b/tests/flat/snack.nix
@@ -0,0 +1,6 @@
+# This "snack" passing is ugly, figure out a nice way of passing snack-lib
+with (import ../../nix {}).snack-lib;
+let
+  modB = makeModuleSpec "B" [] false;
+  modA = makeModuleSpec "A" [modB] true;
+in linkModuleObjects ./. modA
diff --git a/tests/nested/Foo/A.hs b/tests/nested/Foo/A.hs
new file mode 100644
index 0000000..d0fe9b9
--- /dev/null
+++ b/tests/nested/Foo/A.hs
@@ -0,0 +1,3 @@
+import Foo.B.C
+
+main = putStrLn var
diff --git a/tests/nested/Foo/B/C.hs b/tests/nested/Foo/B/C.hs
new file mode 100644
index 0000000..0e77cb9
--- /dev/null
+++ b/tests/nested/Foo/B/C.hs
@@ -0,0 +1,3 @@
+module Foo.B.C where
+
+var = "Hello, World!"
diff --git a/tests/nested/README.md b/tests/nested/README.md
new file mode 100644
index 0000000..8deb2cc
--- /dev/null
+++ b/tests/nested/README.md
@@ -0,0 +1,4 @@
+# Nested
+
+Make sure that nested modules (e.g. `Foo.A` and `Foo.B.C`) can be built into an
+executable
diff --git a/tests/nested/snack.nix b/tests/nested/snack.nix
new file mode 100644
index 0000000..e6345b7
--- /dev/null
+++ b/tests/nested/snack.nix
@@ -0,0 +1,6 @@
+# This "snack" passing is ugly, figure out a nice way of passing snack-lib
+with (import ../../nix {}).snack-lib;
+let
+  modB = makeModuleSpec "Foo.B.C" [] false;
+  modA = makeModuleSpec "Foo.A" [modB] true;
+in linkModuleObjects ./. modA