clanServices/zerotier: Add eval tests

Add eval tests to the zerotier clanService module.

The vm module is a stub that acts as an api for the `generate-test-vars`
script, as that currently only works with a vm, not with an eval test.

This checks, if all the peers pick up their respective configuration
correctly. Without running the service itself.

clanServices/zerotier/tests/eval-tests.nix

@@ -0,0 +1,73 @@
+{
+  module,
+  clanLib,
+  ...
+}:
+let
+  testFlake = clanLib.buildClan {
+    directory = ./vm;
+
+    machines.jon = {
+      nixpkgs.hostPlatform = "x86_64-linux";
+    };
+    machines.sara = {
+      nixpkgs.hostPlatform = "x86_64-linux";
+    };
+    machines.bam = {
+      nixpkgs.hostPlatform = "x86_64-linux";
+    };
+
+    modules.zerotier = module;
+
+    inventory.instances = {
+      zerotier = {
+        module.name = "zerotier";
+
+        roles.peer.tags.all = { };
+        roles.moon.machines.sara.settings.stableEndpoints = [ "10.0.0.3/9993" ];
+        roles.controller.machines.bam = { };
+      };
+    };
+  };
+in
+{
+  test_peers = {
+    expr = {
+      hasNetworkIds = testFlake.nixosConfigurations.jon.config.services.zerotierone.joinNetworks;
+      isController =
+        testFlake.nixosConfigurations.jon.config.clan.core.networking.zerotier.controller.enable;
+      networkName = testFlake.nixosConfigurations.jon.config.clan.core.networking.zerotier.name;
+    };
+    expected = {
+      hasNetworkIds = [ "0e28cb903344475e" ];
+      isController = false;
+      networkName = "zerotier";
+    };
+  };
+  test_moon = {
+    expr = {
+      hasNetworkIds = testFlake.nixosConfigurations.sara.config.services.zerotierone.joinNetworks;
+      isController =
+        testFlake.nixosConfigurations.sara.config.clan.core.networking.zerotier.controller.enable;
+      networkName = testFlake.nixosConfigurations.sara.config.clan.core.networking.zerotier.name;
+    };
+    expected = {
+      hasNetworkIds = [ "0e28cb903344475e" ];
+      isController = false;
+      networkName = "zerotier";
+    };
+  };
+  test_controller = {
+    expr = {
+      hasNetworkIds = testFlake.nixosConfigurations.bam.config.services.zerotierone.joinNetworks;
+      isController =
+        testFlake.nixosConfigurations.bam.config.clan.core.networking.zerotier.controller.enable;
+      networkName = testFlake.nixosConfigurations.bam.config.clan.core.networking.zerotier.name;
+    };
+    expected = {
+      hasNetworkIds = [ "0e28cb903344475e" ];
+      isController = true;
+      networkName = "zerotier";
+    };
+  };
+}