test: Add hydraJobs.tests.functional_symlinked-home

(cherry picked from commit 628c11d237)

tests/nixos/default.nix

@@ -145,6 +145,8 @@ in
 
   functional_root = runNixOSTestFor "x86_64-linux" ./functional/as-root.nix;
 
+  functional_symlinked-home = runNixOSTestFor "x86_64-linux" ./functional/symlinked-home.nix;
+
   user-sandboxing = runNixOSTestFor "x86_64-linux" ./user-sandboxing;
 
   fetchurl = runNixOSTestFor "x86_64-linux" ./fetchurl.nix;

tests/nixos/functional/symlinked-home.nix

@@ -0,0 +1,36 @@
+/**
+  This test runs the functional tests on a NixOS system where the home directory
+  is symlinked to another location.
+
+  The purpose of this test is to find cases where Nix uses low-level operations
+  that don't support symlinks on paths that include them.
+
+  It is not a substitute for more intricate, use case-specific tests, but helps
+  catch common issues.
+*/
+# TODO: add symlinked tmpdir
+{ ... }:
+{
+  name = "functional-tests-on-nixos_user_symlinked-home";
+
+  imports = [ ./common.nix ];
+
+  nodes.machine = {
+    users.users.alice = { isNormalUser = true; };
+  };
+
+  testScript = ''
+    machine.wait_for_unit("multi-user.target")
+    with subtest("prepare symlinked home"):
+      machine.succeed("""
+        (
+          set -x
+          mv /home/alice /home/alice.real
+          ln -s alice.real /home/alice
+        ) 1>&2
+      """)
+    machine.succeed("""
+      su --login --command "run-test-suite" alice >&2
+    """)
+  '';
+}