add nt.units

nt/default.nix

@@ -5,5 +5,6 @@ mix.newMixture inputs (mixture: {
   ];
   submods.public = [
     ./mix
+    ./units
   ];
 })

nt/units/README.md

@@ -0,0 +1 @@
+# Unit Testing For Nix

nt/units/default.nix

@@ -0,0 +1,52 @@
+{
+  flake,
+  this,
+  ...
+}: let
+  inherit
+    (builtins)
+    derivation
+    getFlake
+    ;
+
+  inherit
+    (this)
+    genAttrs
+    ;
+
+  # TODO: rewrite nix-unit to lose dependency
+  nix-unit-flake = getFlake "github.com:nix-community/nix-unit?rev=5e224c19c7087daebb7f7ac95acdfdcc08ea7433";
+
+  forAllSystems = genAttrs [
+    "aarch64-darwin"
+    "aarch64-linux"
+    "x86_64-darwin"
+    "x86_64-linux"
+  ];
+in {
+  tests.testPass = {
+    expr = 3;
+    expected = 4;
+  };
+
+  checks = forAllSystems (system: let
+    nix-unit = "${nix-unit-flake.packages.${system}.default}/bin/nix-unit";
+  in {
+    default = derivation {
+      inherit system;
+      name = "nt-units";
+      builder = "/bin/sh";
+
+      args = [
+        "-c"
+        ''export HOME="$(realpath .)"; ${nix-unit} --eval-store "$HOME" --flake ${flake}#tests --extra-experimental-features flakes --extra-experimental-features nix-command --extra-experimental-features pipe-operators; touch $out''
+      ];
+
+      # XXX: TODO: is nix-unit-flake built in the sandbox (probably not right?)
+      # fixed-output-derivation by using output* options
+      # outputHashMode = "flat";
+      # outputHashAlgo = "sha256";
+      # outputHash = "";
+    };
+  });
+}