numbat: Allow specifying a path for initFile

tests/modules/programs/numbat/default.nix

@@ -1,4 +1,5 @@
 {
   numbat-example-config = ./example-config.nix;
   numbat-empty-config = ./empty-config.nix;
+  numbat-external-initfile = ./external-initfile.nix;
 }

tests/modules/programs/numbat/external-initfile.nix

@@ -0,0 +1,27 @@
+{
+  config,
+  pkgs,
+  ...
+}:
+let
+  configDir =
+    if pkgs.stdenv.hostPlatform.isDarwin then
+      "Library/Application Support/numbat"
+    else
+      ".config/numbat";
+in
+{
+  programs.numbat = {
+    enable = true;
+    package = config.lib.test.mkStubPackage { };
+    initFile = ./init.nbt;
+  };
+
+  nmt.script = ''
+    assertFileExists 'home-files/${configDir}/init.nbt'
+    assertFileContent $(normalizeStorePaths 'home-files/${configDir}/init.nbt') \
+      ${builtins.toFile "expected-init.nbt" ''
+        unit kohm: ElectricResistance = kV/A
+      ''}
+  '';
+}

tests/modules/programs/numbat/init.nbt

@@ -0,0 +1 @@
+unit kohm: ElectricResistance = kV/A