tests: reduce number of downloads

This replaces some derivation outputs by simple strings rather than
full Nix store paths. This removes the need to download the whole
derivation when all we need is a static string.

tests/modules/programs/bash/session-variables-expected.txt

@@ -1,6 +1,6 @@
 # -*- mode: sh -*-
 
-. "@homeDirectory@/.nix-profile/etc/profile.d/hm-session-vars.sh"
+. "/home/testuser/.nix-profile/etc/profile.d/hm-session-vars.sh"
 
 export V1="v1"
 export V2="v2-v1"

tests/modules/programs/bash/session-variables.nix

@@ -13,16 +13,13 @@ with lib;
       };
     };
 
+    home.homeDirectory = "/home/testuser";
+
     nmt.script = ''
       assertFileExists home-files/.profile
       assertFileContent \
         home-files/.profile \
-        ${
-          pkgs.substituteAll {
-            src = ./session-variables-expected.txt;
-            inherit (config.home) homeDirectory;
-          }
-        }
+        ${./session-variables-expected.txt}
     '';
   };
 }