diff --git a/.envrc b/.envrc
new file mode 100644
index 0000000..3550a30
--- /dev/null
+++ b/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/.github/workflows/Test.yml b/.github/workflows/Test.yml
new file mode 100644
index 0000000..d7c12ac
--- /dev/null
+++ b/.github/workflows/Test.yml
@@ -0,0 +1,31 @@
+# This is a basic workflow to help you get started with Actions
+
+name: CI
+
+# Controls when the workflow will run
+on:
+  # Triggers the workflow on push or pull request events but only for the "main" branch
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# A workflow run is made up of one or more jobs that can run sequentially or in parallel
+jobs:
+  # This workflow contains a single job called "build"
+  build:
+    # The type of runner that the job will run on
+    runs-on: ubuntu-latest
+
+    # Steps represent a sequence of tasks that will be executed as part of the job
+    steps:
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v4
+      - name: Install Nix
+        uses: cachix/install-nix-action@v17
+      - name: Build and test
+        run: nix build
+
diff --git a/.gitignore b/.gitignore
index 411a136..441bc38 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,3 +30,6 @@ _opam/
 
 # nix result symlink
 result
+
+# direnv symlinks for dev environments
+.direnv
diff --git a/flake.nix b/flake.nix
index bf41a18..cc49e4b 100644
--- a/flake.nix
+++ b/flake.nix
@@ -11,10 +11,16 @@
         pkgs = nixpkgs.legacyPackages.${system};
         on = opam-nix.lib.${system};
         scope =
-          on.buildOpamProject { } package ./. { ocaml-system = "*"; };
+          on.buildDuneProject { resolveArgs.with-test = true; } package ./. { ocaml-base-compiler = "*"; };
         overlay = final: prev:
           {
             # Your overrides go here
+            cpspg = prev.cpspg.override {
+              doCheck = true;
+              checkPhase = ''
+                dune runtest
+              '';
+            };
 
           };
       in rec {
@@ -25,23 +31,8 @@
           cpspg = default;
         };
 
-        devShells.default = with pkgs; pkgs.mkShell {
-          buildInputs = [ 
-              # Source file formatting
-              nixpkgs-fmt
-              ocamlformat
-              # For `dune build --watch ...`
-              fswatch
-              # For `dune build @doc`
-              ocamlPackages.odoc
-              # OCaml editor support
-              ocamlPackages.ocaml-lsp
-              # Nicely formatted types on hover
-              ocamlPackages.ocamlformat-rpc-lib
-              # Fancy REPL thing
-              ocamlPackages.utop
-              legacyPackages.cpspg
-          ];
+        devShells.default = pkgs.mkShell {
+          buildInputs = packages.default.buildInputs;
         };
       });
 }