refactor(clanServices): add example of eval test

clanServices/zerotier-redux/tests/eval-tests.nix

@@ -0,0 +1,53 @@
+{
+  module,
+  clanLib,
+  ...
+}:
+let
+  testFlake = clanLib.buildClan {
+    # Point to the folder of the module
+    # TODO: make this optional in buildClan
+    directory = ./..;
+
+    # Create some test machines
+    machines.jon = {
+      nixpkgs.hostPlatform = "x86_64-linux";
+    };
+    machines.sara = {
+      nixpkgs.hostPlatform = "x86_64-linux";
+    };
+
+    # Register the module for the test
+    inventory.modules.zerotier-redux = module;
+
+    # Use the module in the test
+    inventory.instances = {
+      "zero" = {
+        module.name = "zerotier-redux";
+
+        roles.peer.machines.jon = { };
+      };
+    };
+  };
+  # NOTE:
+  # If you wonder why 'self-zerotier-redux':
+  # A local module has prefix 'self', otherwise it is the name of the 'input'
+  # The rest is the name of the service as in the instance 'module.name';
+  #
+  # -> ${module.input}-${module.name}
+  # In this case it is 'self-zerotier-redux'
+  # This is usually only used internally, but we can use it to test the evaluation of service module in isolation
+  # evaluatedService =
+  #   testFlake.clanInternals.inventoryClass.distributedServices.importedModulesEvaluated.self-zerotier-redux.config;
+in
+{
+  test_simple = {
+    inherit testFlake;
+
+    expr = {
+    };
+    expected = {
+
+    };
+  };
+}