backend/tests/assistantRoute.test.js

import {
  ASSISTANT_MAX_TOKENS,
  buildSystemPrompt,
  resolveAssistantLanguage,
} from "../routes/assistantRoute.js";

describe("assistant route localization helpers", () => {
  it("prefers selected_language when it is supported", () => {
    expect(resolveAssistantLanguage({ lang: "en", selected_language: "ta" })).toBe("ta");
  });

  it("falls back to lang when selected_language is missing or unsupported", () => {
    expect(resolveAssistantLanguage({ lang: "hi" })).toBe("hi");
    expect(resolveAssistantLanguage({ lang: "bn", selected_language: "xx" })).toBe("bn");
  });

  it("defaults to English for unsupported payloads", () => {
    expect(resolveAssistantLanguage({ lang: "xx", selected_language: "yy" })).toBe("en");
  });

  it("builds a prompt that forces the selected language", () => {
    const prompt = buildSystemPrompt("ml");
    expect(prompt).toContain("user's selected language: Malayalam");
    expect(prompt).toContain("reply in Malayalam");
  });

  it("uses the expanded multilingual token limit", () => {
    expect(ASSISTANT_MAX_TOKENS).toBe(4096);
  });
});