fix nt depends on pipe-operators

flake/nix-unit.nix

@@ -5,19 +5,32 @@
   ...
 }: let
   inherit
-    (deps)
-    nixpkgs
-    nix-unit
+    (builtins)
+    concatStringsSep
     ;
 
   inherit
     (this.util)
     forAllSystems
     ;
+
+  inherit
+    (deps)
+    nixpkgs
+    nix-unit
+    ;
+in let
+  enable-experimental = concatStringsSep " " [
+    "flakes"
+    "nix-command"
+    "pipe-operators"
+  ];
 in {
-  checks = forAllSystems (system: {
+  # XXX: TODO: assert false || throw "TEST: type of flake is \"${builtins.typeOf flake}\""
+  checks = forAllSystems (
+    system: pkgs: {
       default =
-      nixpkgs.legacyPackages.${system}.runCommand "tests"
+        pkgs.runCommand "tests"
         {
           nativeBuildInputs = [nix-unit.packages.${system}.default];
         }
@@ -25,10 +38,11 @@ in {
           export HOME="$(realpath .)"
           # The nix derivation must be able to find all used inputs in the nix-store because it cannot download it during buildTime.
           nix-unit --eval-store "$HOME"                            \
-          --extra-experimental-features flakes \
+            --extra-experimental-features "${enable-experimental}" \
             --override-input nixpkgs ${nixpkgs}                    \
-          --flake ${flake}#tests
+            --flake ${flake}\#tests
           touch $out
         '';
-  });
+    }
+  );
 }