test: add test file for multiplayerGameService

Covers generateMultiplayerQuestions: question count, option structure,
correct answer inclusion, correctOptionId integrity, prompt/gloss
passthrough, DB call arguments, and error propagation.

apps/api/src/services/multiplayerGameService.test.ts

@@ -0,0 +1,125 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+
+vi.mock("@lila/db", () => ({ getGameTerms: vi.fn(), getDistractors: vi.fn() }));
+
+import { getGameTerms, getDistractors } from "@lila/db";
+import { generateMultiplayerQuestions } from "./multiplayerGameService.js";
+
+const mockGetGameTerms = vi.mocked(getGameTerms);
+const mockGetDistractors = vi.mocked(getDistractors);
+
+const fakeTerms = [
+  { termId: "t1", sourceText: "dog", targetText: "cane", sourceGloss: null },
+  { termId: "t2", sourceText: "cat", targetText: "gatto", sourceGloss: null },
+  {
+    termId: "t3",
+    sourceText: "house",
+    targetText: "casa",
+    sourceGloss: "a building for living in",
+  },
+];
+
+beforeEach(() => {
+  vi.clearAllMocks();
+  mockGetGameTerms.mockResolvedValue(fakeTerms);
+  mockGetDistractors.mockResolvedValue(["wrong1", "wrong2", "wrong3"]);
+});
+
+describe("generateMultiplayerQuestions", () => {
+  it("returns the correct number of questions", async () => {
+    const questions = await generateMultiplayerQuestions();
+
+    expect(questions).toHaveLength(3);
+  });
+
+  it("each question has exactly 4 options", async () => {
+    const questions = await generateMultiplayerQuestions();
+
+    for (const question of questions) {
+      expect(question.options).toHaveLength(4);
+    }
+  });
+
+  it("each question has a unique questionId", async () => {
+    const questions = await generateMultiplayerQuestions();
+    const ids = questions.map((q) => q.questionId);
+
+    expect(new Set(ids).size).toBe(ids.length);
+  });
+
+  it("options have sequential optionIds 0-3", async () => {
+    const questions = await generateMultiplayerQuestions();
+
+    for (const question of questions) {
+      const optionIds = question.options.map((o) => o.optionId);
+      expect(optionIds).toEqual([0, 1, 2, 3]);
+    }
+  });
+
+  it("the correct answer is always among the options", async () => {
+    const questions = await generateMultiplayerQuestions();
+
+    for (let i = 0; i < questions.length; i++) {
+      const question = questions[i]!;
+      const correctText = fakeTerms[i]!.targetText;
+      const optionTexts = question.options.map((o) => o.text);
+
+      expect(optionTexts).toContain(correctText);
+    }
+  });
+
+  it("correctOptionId points to the option whose text matches the correct answer", async () => {
+    const questions = await generateMultiplayerQuestions();
+
+    for (let i = 0; i < questions.length; i++) {
+      const question = questions[i]!;
+      const correctText = fakeTerms[i]!.targetText;
+      const correctOption = question.options.find(
+        (o) => o.optionId === question.correctOptionId,
+      );
+
+      expect(correctOption?.text).toBe(correctText);
+    }
+  });
+
+  it("sets the prompt from the source text", async () => {
+    const questions = await generateMultiplayerQuestions();
+
+    expect(questions[0]!.prompt).toBe("dog");
+    expect(questions[1]!.prompt).toBe("cat");
+    expect(questions[2]!.prompt).toBe("house");
+  });
+
+  it("passes gloss through (null or string)", async () => {
+    const questions = await generateMultiplayerQuestions();
+
+    expect(questions[0]!.gloss).toBeNull();
+    expect(questions[2]!.gloss).toBe("a building for living in");
+  });
+
+  it("calls getGameTerms with the multiplayer defaults", async () => {
+    await generateMultiplayerQuestions();
+
+    expect(mockGetGameTerms).toHaveBeenCalledWith(
+      "en",
+      "it",
+      "noun",
+      "easy",
+      3,
+    );
+  });
+
+  it("calls getDistractors once per question", async () => {
+    await generateMultiplayerQuestions();
+
+    expect(mockGetDistractors).toHaveBeenCalledTimes(3);
+  });
+
+  it("propagates unexpected errors from getGameTerms", async () => {
+    mockGetGameTerms.mockRejectedValue(new Error("connection refused"));
+
+    await expect(generateMultiplayerQuestions()).rejects.toThrow(
+      "connection refused",
+    );
+  });
+});