nixosTests.nscd: test unscd as well

This shows that external nss module resolution is broken with unscd.

nixos/tests/nscd.nix

@@ -14,80 +14,109 @@ in
 {
   name = "nscd";
 
-  nodes.machine = { lib, ... }: {
+  nodes.machine = { pkgs, ... }: {
     imports = [ common/user-account.nix ];
     networking.extraHosts = ''
       2001:db8::1 somehost.test
       192.0.2.1 somehost.test
     '';
+
+    specialisation = {
+      withUnscd.configuration = { ... }: {
+        services.nscd.package = pkgs.unscd;
+      };
+    };
   };
 
-  testScript = ''
-    start_all()
-    machine.wait_for_unit("default.target")
-
-    # Regression test for https://github.com/NixOS/nixpkgs/issues/50273
-    with subtest("DynamicUser actually allocates a user"):
-        assert "iamatest" in machine.succeed(
-            "systemd-run --pty --property=Type=oneshot --property=DynamicUser=yes --property=User=iamatest whoami"
-        )
-
-    # Test resolution of somehost.test with getent', to make sure we go via nscd
-    with subtest("host lookups via nscd"):
-        # ahosts
-        output = machine.succeed("${getent'} ahosts somehost.test")
-        assert "192.0.2.1" in output
-        assert "2001:db8::1" in output
-
-        # ahostsv4
-        output = machine.succeed("${getent'} ahostsv4 somehost.test")
-        assert "192.0.2.1" in output
-        assert "2001:db8::1" not in output
-
-        # ahostsv6
-        output = machine.succeed("${getent'} ahostsv6 somehost.test")
-        assert "192.0.2.1" not in output
-        assert "2001:db8::1" in output
-
-        # reverse lookups (hosts)
-        assert "somehost.test" in machine.succeed("${getent'} hosts 2001:db8::1")
-        assert "somehost.test" in machine.succeed("${getent'} hosts 192.0.2.1")
-
-
-    # Test host resolution via nss modules works
-    # We rely on nss-myhostname in this case, which resolves *.localhost and
-    # _gateway.
-    # We don't need to use getent' here, as non-glibc nss modules can only be
-    # discovered via nscd.
-    with subtest("nss-myhostname provides hostnames (ahosts)"):
-        # ahosts
-        output = machine.succeed("getent ahosts foobar.localhost")
-        assert "::1" in output
-        assert "127.0.0.1" in output
-
-        # ahostsv4
-        output = machine.succeed("getent ahostsv4 foobar.localhost")
-        assert "::1" not in output
-        assert "127.0.0.1" in output
-
-        # ahostsv6
-        output = machine.succeed("getent ahostsv6 foobar.localhost")
-        assert "::1" in output
-        assert "127.0.0.1" not in output
-
-        # ahosts
-        output = machine.succeed("getent ahosts _gateway")
-
-        # returns something like the following:
-        # 10.0.2.2        STREAM _gateway
-        # 10.0.2.2        DGRAM
-        # 10.0.2.2        RAW
-        # fe80::2         STREAM
-        # fe80::2         DGRAM
-        # fe80::2         RAW
-
-        # Verify we see both ip addresses
-        assert "10.0.2.2" in output
-        assert "fe80::2" in output
-  '';
+  testScript = { nodes, ... }:
+    let
+      specialisations = "${nodes.machine.system.build.toplevel}/specialisation";
+    in
+    ''
+      # Regression test for https://github.com/NixOS/nixpkgs/issues/50273
+      def test_dynamic_user():
+          with subtest("DynamicUser actually allocates a user"):
+              assert "iamatest" in machine.succeed(
+                  "systemd-run --pty --property=Type=oneshot --property=DynamicUser=yes --property=User=iamatest whoami"
+              )
+
+      # Test resolution of somehost.test with getent', to make sure we go via nscd
+      def test_host_lookups():
+          with subtest("host lookups via nscd"):
+              # ahosts
+              output = machine.succeed("${getent'} ahosts somehost.test")
+              assert "192.0.2.1" in output
+              assert "2001:db8::1" in output
+
+              # ahostsv4
+              output = machine.succeed("${getent'} ahostsv4 somehost.test")
+              assert "192.0.2.1" in output
+              assert "2001:db8::1" not in output
+
+              # ahostsv6
+              output = machine.succeed("${getent'} ahostsv6 somehost.test")
+              assert "192.0.2.1" not in output
+              assert "2001:db8::1" in output
+
+              # reverse lookups (hosts)
+              assert "somehost.test" in machine.succeed("${getent'} hosts 2001:db8::1")
+              assert "somehost.test" in machine.succeed("${getent'} hosts 192.0.2.1")
+
+      # Test host resolution via nss modules works
+      # We rely on nss-myhostname in this case, which resolves *.localhost and
+      # _gateway.
+      # We don't need to use getent' here, as non-glibc nss modules can only be
+      # discovered via nscd.
+      def test_nss_myhostname():
+          with subtest("nss-myhostname provides hostnames (ahosts)"):
+              # ahosts
+              output = machine.succeed("getent ahosts foobar.localhost")
+              assert "::1" in output
+              assert "127.0.0.1" in output
+
+              # ahostsv4
+              output = machine.succeed("getent ahostsv4 foobar.localhost")
+              assert "::1" not in output
+              assert "127.0.0.1" in output
+
+              # ahostsv6
+              output = machine.succeed("getent ahostsv6 foobar.localhost")
+              assert "::1" in output
+              assert "127.0.0.1" not in output
+
+              # ahosts
+              output = machine.succeed("getent ahosts _gateway")
+
+              # returns something like the following:
+              # 10.0.2.2        STREAM _gateway
+              # 10.0.2.2        DGRAM
+              # 10.0.2.2        RAW
+              # fe80::2         STREAM
+              # fe80::2         DGRAM
+              # fe80::2         RAW
+
+              # Verify we see both ip addresses
+              assert "10.0.2.2" in output
+              assert "fe80::2" in output
+
+      start_all()
+      machine.wait_for_unit("default.target")
+
+      # Test all tests with glibc-nscd.
+      test_dynamic_user()
+      test_host_lookups()
+      test_nss_myhostname()
+
+      with subtest("unscd"):
+          machine.succeed('${specialisations}/withUnscd/bin/switch-to-configuration test')
+          machine.wait_for_unit("default.target")
+
+          # known to fail, unscd doesn't load external NSS modules
+          # test_dynamic_user()
+
+          test_host_lookups()
+
+          # known to fail, unscd doesn't load external NSS modules
+          # test_nss_myhostname()
+    '';
 })