test: add integration nixos tests

flake.nix

@@ -17,7 +17,7 @@
             vendorHash = null;
             pname = "leng";
             version = "1.5.3";
-            src = ./.;
+            src = nixpkgs.lib.sources.cleanSource ./.;
           };
           default = leng;
         };
@@ -49,8 +49,15 @@
           default = leng;
         };
 
-      })) //
+        checks = {
+          inherit (self.packages.${system}) leng;
+          metrics-api = pkgs.callPackage ./nixos-tests/metrics-api.nix { inherit self; };
+          systemctl-start = pkgs.callPackage ./nixos-tests/systemctl-start.nix { inherit self; };
+          custom-dns = pkgs.callPackage ./nixos-tests/custom-dns.nix { inherit self; };
+        };
 
+      }))
+    //
     {
       nixosModules.default = { pkgs, lib, config, ... }:
         with lib;
@@ -91,7 +98,7 @@
           ## implementation
           config = mkIf cfg.enable {
             environment = {
-              etc."leng.toml".source = toml.generate "leng.toml" cfg.configuration;
+              etc."leng.toml".source = { blocking.sourcesStore = "/var/lib/leng-sources";} // (toml.generate "leng.toml" cfg.configuration);
               systemPackages = [ cfg.package ];
             };
 
@@ -122,9 +129,9 @@
             };
             assertions = [
               {
-                assertion = cfg.configuration.blocking.sourcesStore == "/var/lib/leng-sources";
+                assertion = (cfg.configuration ? "blocking" && cfg.configuration.blocking ? "sourcesStore");
                 message = ''
-                  `services.leng.configuration.blocking.sourcesStore` should be set to `var/lib/leng-sources`, but it is set to ${cfg.configuration.blocking.sourcesStore}.
+                  `services.leng.configuration.blocking.sourcesStore` should be set to a directory leng can write to, but it is not set.
                 '';
               }
             ];

nixos-tests/custom-dns.nix

@@ -0,0 +1,44 @@
+{ self, pkgs, home-manager, ... }:
+let
+  nixpkgs = self.inputs.nixpkgs;
+in
+(nixpkgs.lib.nixos.runTest {
+  hostPkgs = pkgs;
+  defaults.documentation.enable = false;
+  node.specialArgs = { inherit self; };
+
+  name = "leng-custom-dns";
+
+  nodes = {
+    server = { config, pkgs, ... }: {
+      imports = [ self.nixosModules.default ];
+      # Open the default port for `postgrest` in the firewall
+      networking.firewall.allowedUDPPorts = [ 53 ];
+
+      services.leng.enable = true;
+      services.leng.configuration = {
+        blocking.sourcesStore = "/tmp";
+        customdnsrecords = [
+          "example.com    IN A   1.2.3.4"
+        ];
+      };
+    };
+
+    client = { pkgs, ... }: {
+      environment.systemPackages = [ pkgs.dig ];
+    };
+  };
+
+  testScript =
+    ''
+      start_all()
+
+      server.wait_for_unit("leng", timeout=10)
+      server.wait_for_open_port(53)
+
+      client.succeed(
+        "dig @server example.com | grep -o '1.2.3.4' "
+      )
+    '';
+
+}).config.result

nixos-tests/metrics-api.nix

@@ -0,0 +1,42 @@
+{ self, pkgs, home-manager, ... }:
+let
+  nixpkgs = self.inputs.nixpkgs;
+  httpPort = 9243;
+in
+(nixpkgs.lib.nixos.runTest {
+  hostPkgs = pkgs;
+  defaults.documentation.enable = false;
+  node.specialArgs = { inherit self; };
+
+  name = "leng-systemctl-start";
+
+  nodes = {
+    server = { config, pkgs, ... }: {
+      imports = [ self.nixosModules.default ];
+      # Open the default port for `postgrest` in the firewall
+      networking.firewall.allowedTCPPorts = [ httpPort ];
+
+      services.leng.enable = true;
+      services.leng.configuration = {
+        metrics.enabled = true;
+        api = "0.0.0.0:${toString httpPort}";
+        blocking.sourcesStore="/tmp";
+      };
+    };
+
+    client = {};
+  };
+
+  testScript =
+    ''
+      start_all()
+
+      server.wait_for_unit("leng", timeout=10)
+      server.wait_for_open_port(${toString httpPort})
+
+      actual = client.succeed(
+        "curl http://server:${toString httpPort}/metrics | grep -o 'go_gc_duration_seconds' "
+      )
+    '';
+
+}).config.result

nixos-tests/systemctl-start.nix

@@ -0,0 +1,34 @@
+{ self, pkgs, home-manager, ... }:
+let
+  nixpkgs = self.inputs.nixpkgs;
+in
+(nixpkgs.lib.nixos.runTest {
+  hostPkgs = pkgs;
+  defaults.documentation.enable = false;
+  node.specialArgs = { inherit self; };
+
+  name = "leng-metrics-api";
+
+  nodes = {
+    server = { config, pkgs, ... }: {
+      imports = [ self.nixosModules.default ];
+
+      services.leng.enable = true;
+      services.leng.configuration = {
+        blocking.sourcesStore="/tmp";
+      };
+    };
+
+    client = { };
+  };
+
+  testScript =
+    ''
+      start_all()
+
+      server.wait_for_unit("leng", timeout=10)
+
+      server.succeed("systemctl status leng")
+    '';
+
+}).config.result