reduce impure tests to just instantiate the template

checks/impure/flake-module.nix

@@ -0,0 +1,40 @@
+{ self, ... }: {
+  perSystem = { pkgs, lib, ... }:
+    let
+      impureChecks = {
+        check-clan-template = pkgs.writeShellScriptBin "check-clan-template" ''
+          #!${pkgs.bash}/bin/bash
+          set -euo pipefail
+          export TMPDIR=$(${pkgs.coreutils}/bin/mktemp -d)
+          trap "${pkgs.coreutils}/bin/chmod -R +w '$TMPDIR'; ${pkgs.coreutils}/bin/rm -rf '$TMPDIR'" EXIT
+          export PATH="${lib.makeBinPath [
+            pkgs.gitMinimal
+            pkgs.openssh
+            pkgs.nix
+          ]}"
+
+          cd $TMPDIR
+
+          echo initialize new clan
+          nix flake init -t ${self}#new-clan
+
+          echo ensure flake outputs can be listed
+          nix flake show
+        '';
+      };
+    in
+    {
+      packages =
+        impureChecks // {
+          # a script that executes all other checks
+          impure-checks = pkgs.writeShellScriptBin "impure-checks" ''
+            #!${pkgs.bash}/bin/bash
+            set -euo pipefail
+            ${lib.concatMapStringsSep "\n" (name: ''
+              echo -e "\n\nrunning check ${name}\n"
+              ${impureChecks.${name}}/bin/*
+            '') (lib.attrNames impureChecks)}
+          '';
+        };
+    };
+}