diff --git a/default.nix b/default.nix
index f72ea93..3431a13 100644
--- a/default.nix
+++ b/default.nix
@@ -1,15 +1,22 @@
-{
-  pkgs ? (import <nixpkgs> {}),
-  ruby ? pkgs.ruby_2_6,
-  bundler ? (pkgs.bundler.override { inherit ruby; }),
-  nix ? pkgs.nix,
-  nix-prefetch-git ? pkgs.nix-prefetch-git,
+{ pkgs ? (import <nixpkgs> {})
+, ruby ? pkgs.ruby_2_6
+, bundler ? (pkgs.bundler.override { inherit ruby; })
+, nix ? pkgs.nix
+, nix-prefetch-git ? pkgs.nix-prefetch-git
+, rake ? pkgs.rubyPackages.rake
+, minitest ? pkgs.rubyPackages.minitest
+, nix-prefetch-scripts ? pkgs.nix-prefetch-scripts
 }:
-pkgs.stdenv.mkDerivation rec {
+let
+ srcWithout = rootPath: ignoredPaths:
+   let
+     ignoreStrings = map (path: toString path ) ignoredPaths;
+   in
+    builtins.filterSource (path: type: (builtins.all (i: i != path) ignoreStrings)) rootPath;
+in pkgs.stdenv.mkDerivation rec {
   version = "2.5.0";
   name = "bundix";
-  src = ./.;
-  phases = "installPhase";
+  src = srcWithout ./. [ ./.git ./tmp ./result ];
   installPhase = ''
     mkdir -p $out
     makeWrapper $src/bin/bundix $out/bin/bundix \
@@ -22,6 +29,19 @@ pkgs.stdenv.mkDerivation rec {
   nativeBuildInputs = [ pkgs.makeWrapper ];
   buildInputs = [ ruby bundler ];
 
+  checkInputs = [
+    rake
+    minitest
+
+    nix-prefetch-scripts
+    nix
+  ];
+
+  doCheck = true;
+  checkPhase = ''
+    NIX_STATE_DIR=$TMPDIR/var HOME=$TMPDIR rake test
+  '';
+
   meta = {
     inherit version;
     description = "Creates Nix packages from Gemfiles";
diff --git a/shell.nix b/shell.nix
deleted file mode 100644
index c4272fd..0000000
--- a/shell.nix
+++ /dev/null
@@ -1,44 +0,0 @@
-with (import <nixpkgs> {});
-with builtins;
-
-let
-  minitest = buildRubyGem {
-    inherit ruby;
-    gemName = "minitest";
-    type = "gem";
-    version = "5.10.1";
-    source.sha256 = "1yk2m8sp0p5m1niawa3ncg157a4i0594cg7z91rzjxv963rzrwab";
-    gemPath = [];
-  };
-
-  rake = buildRubyGem {
-    inherit ruby;
-    gemName = "rake";
-    type = "gem";
-    version = "12.0.0";
-    source.sha256 = "01j8fc9bqjnrsxbppncai05h43315vmz9fwg28qdsgcjw9ck1d7n";
-    gemPath = [];
-  };
-
- srcWithout = rootPath: ignoredPaths:
-   let
-     ignoreStrings = map (path: toString path ) ignoredPaths;
-   in
-     filterSource (path: type: (all (i: i != path) ignoreStrings)) rootPath;
-in
-  stdenv.mkDerivation {
-  name = "bundix";
-  src = srcWithout ./. [ ./.git ./tmp ./result ];
-  phases = "installPhase";
-  installPhase = ''
-    mkdir -p $out
-    makeWrapper $src/bin/bundix $out/bin/bundix \
-      --prefix PATH : "${nix.out}/bin" \
-      --prefix PATH : "${nix-prefetch-git.out}/bin" \
-      --set GEM_PATH "${bundler}/${bundler.ruby.gemPath}"
-  '';
-
-  nativeBuildInputs = [makeWrapper];
-
-  buildInputs = [bundler ruby minitest rake nix-prefetch-scripts];
-}