dev: Improve support for front end unit tests (#7163)

frontend/app/tests/setup.ts

@@ -0,0 +1,18 @@
+import { config } from "@vue/test-utils";
+import { createI18n } from "vue-i18n";
+
+function loadEnLocales() {
+  // eslint-disable-next-line @typescript-eslint/no-require-imports
+  return require("../lang/messages/en-US.json") as Record<string, string>;
+}
+
+const i18n = createI18n({
+  locale: "en-US",
+  messages: {
+    "en-US": loadEnLocales(),
+  },
+});
+
+config.global.plugins = [...(config.global.plugins ?? []), i18n];
+
+export { i18n };