manual: add test

This checks that the documentation can be built in the context of a
Home Manager configuration.

tests/default.nix

@@ -30,7 +30,7 @@ let
 
       # Avoid including documentation since this will cause
       # unnecessary rebuilds of the tests.
-      manual.manpages.enable = false;
+      manual.manpages.enable = lib.mkDefault false;
 
       imports = [ ./asserts.nix ./big-test.nix ./stubs.nix ];
 
@@ -52,6 +52,7 @@ import nmt {
     ./modules/files
     ./modules/home-environment
     ./modules/misc/fontconfig
+    ./modules/misc/manual
     ./modules/misc/nix
     ./modules/misc/specialisation
     ./modules/programs/aerc

tests/modules/misc/manual/default.nix

@@ -0,0 +1 @@
+{ manual = ./manual.nix; }

tests/modules/misc/manual/manual.nix

@@ -0,0 +1,19 @@
+{ ... }:
+
+{
+  config = {
+    manual = {
+      html.enable = true;
+      manpages.enable = true;
+      json.enable = true;
+    };
+
+    nmt.script = ''
+      assertFileExists home-path/share/doc/home-manager/index.html
+      assertFileExists home-path/share/doc/home-manager/options.html
+      assertFileExists home-path/share/doc/home-manager/options.json
+      assertFileExists home-path/share/man/man1/home-manager.1.gz
+      assertFileExists home-path/share/man/man5/home-configuration.nix.5.gz
+    '';
+  };
+}