add non working test for now

flake.nix

@@ -1,16 +1,22 @@
 {
   inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
-  outputs = { nixpkgs, ... }: let
+  outputs = { nixpkgs, ... }@self: let
     supportedArchitectures = [
       "aarch64-darwin"
       "aarch64-linux"
       "x86_64-darwin"
       "x86_64-linux"
     ];
-  in {
+  in rec {
     packages = nixpkgs.lib.genAttrs supportedArchitectures (system: {
       nix_templater = nixpkgs.legacyPackages.${system}.callPackage ./pkgs/nix_templater {};
     });
-    legacyPackages = nixpkgs.lib.genAttrs supportedArchitectures (system: import ./lib.nix { pkgs = nixpkgs.legacyPackages.${system}; });
+    legacyPackages = nixpkgs.lib.genAttrs supportedArchitectures (system: import ./lib.nix {
+      pkgs = nixpkgs.legacyPackages.${system};
+      nix_templater = packages.${system}.nix_templater;
+    });
+    checks = nixpkgs.lib.genAttrs supportedArchitectures (system: {
+      template = import ./tests/template.nix { inherit legacyPackages system nixpkgs; };
+    });
   };
 }

lib.nix

@@ -1,4 +1,4 @@
-{ pkgs, text_templater }:
+{ pkgs, nix_templater }:
 rec {
   fileContents = file: {
    outPath = "<${builtins.placeholder "nix_template"}${toString file}${builtins.placeholder "nix_template"}>";
@@ -9,7 +9,8 @@ rec {
     pkgs.runCommand name {
       textBeforeTemplate = text;
       script = ''
-        ${text_templater}/bin/text_templater ${builtins.placeholder "out"}/template ${builtins.placeholder "nix_template"} "${outPath}"
+        #!/bin/sh
+        ${nix_templater}/bin/nix_templater ${builtins.placeholder "out"}/template ${builtins.placeholder "nix_template"} "${outPath}"
       '';
       passAsFile = [ "script" "textBeforeTemplate" ];
     } ''
@@ -18,12 +19,4 @@ rec {
       cp $scriptPath $out/bin/${name}
       chmod +x $out/bin/${name}
     '';
-
-  test = template_text {
-    name = "test";
-    text = ''
-      blablabla ${fileContents (pkgs.writeText "lol" "lol")}
-    '';
-    outPath = "./test";
-  };
 }

pkgs/nix_templater/default.nix

@@ -1,6 +1,6 @@
 { writeShellApplication, python3 }:
 writeShellApplication {
-  name = "text_templater";
+  name = "nix_templater";
   runtimeInputs = [
     python3
   ];

tests/template.nix

@@ -0,0 +1,39 @@
+{ legacyPackages, system, nixpkgs }:
+let
+  # this file would usually be outside of the store
+  # but in this test it isn't, because setting it up in other ways is hard :)
+  secret_file = (nixpkgs.legacyPackages.${system}.writeText "secret" "secret");
+in (nixpkgs.lib.nixos.runTest {
+    hostPkgs = nixpkgs.legacyPackages.${system};
+    name = "nix_templates";
+
+    nodes.machine = {config, pkgs, ...}: {
+      config = {
+        systemd.services.testservice = {
+          wantedBy = [ "multi-user.target" ];
+          serviceConfig = {
+            Type = "oneshot";
+            ExecStartPre = "${legacyPackages.${system}.template_text {
+              name = "test";
+              text = ''
+              public text
+              ${legacyPackages.${system}.fileContents secret_file}
+              '';
+              outPath = "./test";
+            }}/bin/test";
+            ExecStart = pkgs.writeScript "test_file_got_templates" ''
+              #!/bin/sh
+              cat ./test | grep -q 'secret'
+            '';
+          };
+        };
+      };
+    };
+
+    testScript = ''
+      start_all()
+      print(machine.execute("uname -a"))
+      machine.wait_for_unit("testservice.service")
+      print(machine.succeed("cat /root/test | grep -q secret"))
+    '';
+  })