test: add environment mocking for unit tests

Author: amanabiy

vite.config.unit.mjs

@@ -9,6 +9,34 @@ import base from "./vite.config.mjs";
 export default defineConfig({
   ...base,
   root: "./",
+  resolve: {
+    alias: {
+      "../internal/environment": "/virtual:environment-mock",
+    },
+  },
+  plugins: [
+    ...(base.plugins || []),
+    {
+      name: "virtual-environment-mock",
+      resolveId(id) {
+        if (id === "/virtual:environment-mock") {
+          return id;
+        }
+      },
+      load(id) {
+        if (id === "/virtual:environment-mock") {
+          // Simple stub - the actual values are mocked when testing
+          return `
+            export const THEME = "stub";
+            export const PACKAGE_SOURCE = "stub";
+            export const PACKAGE_VERSION = "stub";
+            export const SYSTEM = "stub";
+            export const ALWAYS_VISUAL_REFRESH = true;
+          `;
+        }
+      },
+    },
+  ],
   test: {
     include: ["./src/**/__tests__/**/*.test.{ts,tsx}"],
     environment: "jsdom",