feat(FN-4637): complete Step 1 — detect bubblewrap availability

Fusion-Task-Id: FN-4637
Fusion-Task-Lineage: 564c5692-3aaf-4396-9306-a395703cf365

packages/engine/src/__tests__/sandbox/bubblewrap-detect.test.ts

@@ -0,0 +1,83 @@
+import { promisify } from "node:util";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const execMock = vi.fn();
+
+vi.mock("node:child_process", () => ({
+  exec: execMock,
+}));
+
+const originalPlatform = process.platform;
+
+function setPlatform(platform: NodeJS.Platform): void {
+  Object.defineProperty(process, "platform", { value: platform });
+}
+
+describe("detectBwrap", () => {
+  beforeEach(async () => {
+    execMock.mockReset();
+    (execMock as unknown as Record<symbol, unknown>)[promisify.custom] = vi.fn();
+    vi.resetModules();
+    setPlatform(originalPlatform);
+  });
+
+  it("detects bubblewrap on linux and parses version/path", async () => {
+    setPlatform("linux");
+    ((execMock as unknown as Record<symbol, unknown>)[promisify.custom] as ReturnType<typeof vi.fn>).mockResolvedValue({
+      stdout: "/usr/bin/bwrap\nbubblewrap 0.9.0\n",
+      stderr: "",
+    });
+
+    const { detectBwrap } = await import("../../sandbox/bubblewrap-detect.js");
+    const result = await detectBwrap();
+
+    expect(result).toEqual({ available: true, path: "/usr/bin/bwrap", version: "0.9.0" });
+    expect(((execMock as unknown as Record<symbol, unknown>)[promisify.custom] as ReturnType<typeof vi.fn>)).toHaveBeenCalledTimes(1);
+  });
+
+  it("returns unavailable when bwrap is missing", async () => {
+    setPlatform("linux");
+    ((execMock as unknown as Record<symbol, unknown>)[promisify.custom] as ReturnType<typeof vi.fn>).mockRejectedValue(new Error("command not found"));
+
+    const { detectBwrap } = await import("../../sandbox/bubblewrap-detect.js");
+    const result = await detectBwrap();
+
+    expect(result.available).toBe(false);
+    expect(result.reason).toBe("not-installed");
+  });
+
+  it("short-circuits on non-linux platforms", async () => {
+    setPlatform("darwin");
+
+    const { detectBwrap } = await import("../../sandbox/bubblewrap-detect.js");
+    const result = await detectBwrap();
+
+    expect(result).toEqual({ available: false, reason: "not-linux" });
+    expect(((execMock as unknown as Record<symbol, unknown>)[promisify.custom] as ReturnType<typeof vi.fn>)).not.toHaveBeenCalled();
+  });
+
+  it("uses cached result until reset", async () => {
+    setPlatform("linux");
+    ((execMock as unknown as Record<symbol, unknown>)[promisify.custom] as ReturnType<typeof vi.fn>).mockResolvedValue({
+      stdout: "/usr/bin/bwrap\nbwrap 1.0.0\n",
+      stderr: "",
+    });
+
+    const { detectBwrap, resetBwrapDetectCache } = await import("../../sandbox/bubblewrap-detect.js");
+    const first = await detectBwrap();
+    const second = await detectBwrap();
+
+    expect(first).toEqual(second);
+    expect(((execMock as unknown as Record<symbol, unknown>)[promisify.custom] as ReturnType<typeof vi.fn>)).toHaveBeenCalledTimes(1);
+
+    resetBwrapDetectCache();
+    ((execMock as unknown as Record<symbol, unknown>)[promisify.custom] as ReturnType<typeof vi.fn>).mockResolvedValue({
+      stdout: "/opt/bin/bwrap\nbwrap 2.0.0\n",
+      stderr: "",
+    });
+
+    const third = await detectBwrap();
+    expect(third.path).toBe("/opt/bin/bwrap");
+    expect(((execMock as unknown as Record<symbol, unknown>)[promisify.custom] as ReturnType<typeof vi.fn>)).toHaveBeenCalledTimes(2);
+  });
+});