plugins/luasnip: add tests

tests/test-sources/plugins/snippets/luasnip.nix

@@ -0,0 +1,31 @@
+{
+  empty = {
+    plugins.luasnip.enable = true;
+  };
+
+  example = {
+    plugins.luasnip = {
+      enable = true;
+
+      settings = {
+        history = true;
+        updateevents = "TextChanged,TextChangedI";
+        enable_autosnippets = true;
+        ext_opts = {
+          "__rawKey__require('luasnip.util.types').choiceNode".active.virt_text = [
+            [
+              "●"
+              "GruvboxOrange"
+            ]
+          ];
+          "__rawKey__require('luasnip.util.types').insertNode".active.virt_text = [
+            [
+              "●"
+              "GruvboxBlue"
+            ]
+          ];
+        };
+      };
+    };
+  };
+}