create nix test infrastructure

nix/default.nix

@@ -1,15 +1,30 @@
 {
-	ocaml-deps,
-	ocamlPackages,
-	version,
-	...
-}: 
+  lib,
+  ocaml-deps,
+  ocamlPackages,
+  version,
+  debug ? false,
+  ...
+}:
 ocamlPackages.buildDunePackage {
-	pname = "culr";
-	version = "0.1-${version}";
+  pname = "culr";
+  version = "0.1-${version}";
 
-	minimalOCamlVersion = "5.2";
+  minimalOCamlVersion = "5.2";
 
-	src = ./..;
-	buildInputs = ocaml-deps;
+  src = ./..;
+  buildInputs = ocaml-deps;
+
+  buildPhase =
+    if debug
+    then ''
+      runHook preBuild
+      dune build --profile debug -p culr ''${enableParallelBuilding:+-j $NIX_BUILD_CORES}
+      runHook postBuild
+    ''
+    else ''
+      runHook preBuild
+      dune build --profile release -p culr ''${enableParallelBuilding:+-j $NIX_BUILD_CORES}
+      runHook postBuild
+    '';
 }

nix/test.nix

@@ -0,0 +1,20 @@
+{
+  pkgs,
+  lib,
+  culr,
+  version,
+  ...
+}:
+pkgs.stdenvNoCC.mkDerivation {
+  pname = "culr-tests";
+  version = "${version}";
+
+  nativebuildInputs = [culr];
+
+  doCheck = true;
+  checkPhase = ''
+    CULRS="(255,0,0);(0,0,255)"
+    CULR_ORDER=1,0
+    echo "one two three four" | ${lib.getExe culr}
+  '';
+}