1 files changed, 73 insertions, 0 deletions
diff --git a/nixpkgs/nixos/tests/hostname.nix b/nixpkgs/nixos/tests/hostname.nix
new file mode 100644
index 000000000000..dffec956bc0b
--- /dev/null
+++ b/nixpkgs/nixos/tests/hostname.nix
@@ -0,0 +1,73 @@
+{ system ? builtins.currentSystem
+, config ? { }
+, pkgs ? import ../.. { inherit system config; }
+}:
+
+with import ../lib/testing-python.nix { inherit system pkgs; };
+with pkgs.lib;
+
+let
+  makeHostNameTest = hostName: domain: fqdnOrNull:
+    let
+      fqdn = hostName + (optionalString (domain != null) ".${domain}");
+      getStr = str: # maybeString2String
+        let res = builtins.tryEval str;
+        in if (res.success && res.value != null) then res.value else "null";
+    in
+    makeTest {
+      name = "hostname-${fqdn}";
+      meta = with pkgs.lib.maintainers; {
+        maintainers = [ primeos blitz ];
+      };
+
+      nodes.machine = { lib, ... }: {
+        networking.hostName = hostName;
+        networking.domain = domain;
+
+        environment.systemPackages = with pkgs; [
+          inetutils
+        ];
+      };
+
+      testScript = { nodes, ... }: ''
+        start_all()
+
+        machine = ${hostName}
+
+        machine.systemctl("start network-online.target")
+        machine.wait_for_unit("network-online.target")
+
+        # Test if NixOS computes the correct FQDN (either a FQDN or an error/null):
+        assert "${getStr nodes.machine.networking.fqdn}" == "${getStr fqdnOrNull}"
+
+        # The FQDN, domain name, and hostname detection should work as expected:
+        assert "${fqdn}" == machine.succeed("hostname --fqdn").strip()
+        assert "${optionalString (domain != null) domain}" == machine.succeed("dnsdomainname").strip()
+        assert (
+            "${hostName}"
+            == machine.succeed(
+                'hostnamectl status | grep "Static hostname" | cut -d: -f2'
+            ).strip()
+        )
+
+        # 127.0.0.1 and ::1 should resolve back to "localhost":
+        assert (
+            "localhost" == machine.succeed("getent hosts 127.0.0.1 | awk '{print $2}'").strip()
+        )
+        assert "localhost" == machine.succeed("getent hosts ::1 | awk '{print $2}'").strip()
+
+        # 127.0.0.2 should resolve back to the FQDN and hostname:
+        fqdn_and_host_name = "${optionalString (domain != null) "${hostName}.${domain} "}${hostName}"
+        assert (
+            fqdn_and_host_name
+            == machine.succeed("getent hosts 127.0.0.2 | awk '{print $2,$3}'").strip()
+        )
+      '';
+    };
+
+in
+{
+  noExplicitDomain = makeHostNameTest "ahost" null null;
+
+  explicitDomain = makeHostNameTest "ahost" "adomain" "ahost.adomain";
+}