test: add convert string body branch coverage tests

src/__tests__/convert-string-body.test.ts

@@ -0,0 +1,55 @@
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import express from "express";
+import request from "supertest";
+
+vi.mock("node:dns/promises", () => ({
+  default: { lookup: vi.fn() },
+  lookup: vi.fn(),
+}));
+
+let app: express.Express;
+
+beforeEach(async () => {
+  vi.clearAllMocks();
+  vi.resetModules();
+
+  const { renderPdf } = await import("../services/browser.js");
+  vi.mocked(renderPdf).mockResolvedValue({ pdf: Buffer.from("%PDF-1.4 mock"), durationMs: 10 });
+
+  const { convertRouter } = await import("../routes/convert.js");
+  app = express();
+  // Parse application/json as text to produce a string req.body,
+  // exercising the typeof === "string" branches in convert routes.
+  app.use(express.text({ type: "application/json", limit: "500kb" }));
+  app.use("/v1/convert", convertRouter);
+});
+
+describe("convert routes handle string body (branch coverage)", () => {
+  it("POST /v1/convert/html with string body parses it as HTML", async () => {
+    const { renderPdf } = await import("../services/browser.js");
+
+    const res = await request(app)
+      .post("/v1/convert/html")
+      .set("content-type", "application/json")
+      .send("<h1>Hello</h1>");
+
+    expect(res.status).toBe(200);
+    expect(vi.mocked(renderPdf)).toHaveBeenCalledOnce();
+    const html = vi.mocked(renderPdf).mock.calls[0]![0] as string;
+    expect(html).toContain("<h1>Hello</h1>");
+  });
+
+  it("POST /v1/convert/markdown with string body parses it as markdown", async () => {
+    const { renderPdf } = await import("../services/browser.js");
+
+    const res = await request(app)
+      .post("/v1/convert/markdown")
+      .set("content-type", "application/json")
+      .send("# Hello");
+
+    expect(res.status).toBe(200);
+    expect(vi.mocked(renderPdf)).toHaveBeenCalledOnce();
+    const html = vi.mocked(renderPdf).mock.calls[0]![0] as string;
+    expect(html).toContain("Hello");
+  });
+});