test: cover beta fallback update logic

src/infra/update-check.test.ts

@@ -0,0 +1,47 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import { resolveNpmChannelTag } from "./update-check.js";
+
+describe("resolveNpmChannelTag", () => {
+  let versionByTag: Record<string, string | null>;
+
+  beforeEach(() => {
+    versionByTag = {};
+    vi.stubGlobal(
+      "fetch",
+      vi.fn(async (input: RequestInfo | URL) => {
+        const url =
+          typeof input === "string" ? input : input instanceof URL ? input.toString() : input.url;
+        const tag = decodeURIComponent(url.split("/").pop() ?? "");
+        const version = versionByTag[tag] ?? null;
+        return {
+          ok: version != null,
+          status: version != null ? 200 : 404,
+          json: async () => ({ version }),
+        } as Response;
+      }),
+    );
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+  });
+
+  it("falls back to latest when beta is older", async () => {
+    versionByTag.beta = "2026.1.19-beta.1";
+    versionByTag.latest = "2026.1.20-1";
+
+    const resolved = await resolveNpmChannelTag({ channel: "beta", timeoutMs: 1000 });
+
+    expect(resolved).toEqual({ tag: "latest", version: "2026.1.20-1" });
+  });
+
+  it("keeps beta when beta is not older", async () => {
+    versionByTag.beta = "2026.1.20-beta.1";
+    versionByTag.latest = "2026.1.20-1";
+
+    const resolved = await resolveNpmChannelTag({ channel: "beta", timeoutMs: 1000 });
+
+    expect(resolved).toEqual({ tag: "beta", version: "2026.1.20-beta.1" });
+  });
+});