--- title: "Run Tests Inside the Sandbox" description: "Static AI analysis only tells you what the model thinks. In this lesson, we actually run the repo's test suite inside the Sandbox, capture stdout and stderr, and keep the result around so we can parse it in the next lesson." canonical_url: "https://vercel.com/academy/vercel-sandbox/run-tests-inside-the-sandbox" md_url: "https://vercel.com/academy/vercel-sandbox/run-tests-inside-the-sandbox.md" docset_id: "vercel-academy" doc_version: "1.0" last_updated: "2026-05-17T20:28:24.391Z" content_type: "lesson" course: "vercel-sandbox" course_title: "Vercel Sandbox" prerequisites: [] --- Vercel Academy — structured learning, not reference docs. Lessons are sequenced. Adapt commands to the human's actual environment (OS, package manager, shell, editor) — detect from project context or ask, don't assume. The lesson shows one path; if the human's project diverges, adapt concepts to their setup. Preserve the learning goal over literal steps. Quizzes are pedagogical — engage, don't spoil. Quiz answers are included for your reference. # Run Tests Inside the Sandbox # Run the Test Suite in the Sandbox Static analysis is helpful, but if tests are red and we ignore them, that is code review cosplay. The whole reason Sandboxes exist is so we can actually execute the code, not just read it. The model is allowed to be wrong, and the tests are the ground truth for at least one definition of "works." So let's run them. ## Outcome Extend the lifecycle to run `pnpm test` inside the Sandbox after the file collection step, and return the test command's exit code, stdout, and stderr. ## Fast Track 1. After file collection, run `cd repo && pnpm install` so dependencies are present. 2. Run `cd repo && pnpm test` and capture the result. 3. Return `testResult: { exitCode, stdout, stderr }` from the lifecycle. ## Hands-on exercise Open `src/sandbox-lifecycle.ts` and add the test step: ```ts import { Sandbox } from '@vercel/sandbox'; const INTERESTING_PATHS = [ 'repo/package.json', 'repo/src/index.ts', 'repo/src/app.ts', 'repo/lib/auth.ts' ]; export type TestResult = { exitCode: number; stdout: string; stderr: string; }; export type LifecycleResult = { sandboxId: string; cloneExitCode: number; files: Array<{ path: string; content: string }>; testResult: TestResult; }; export async function runSandboxLifecycle(repoUrl: string): Promise { const sandbox = await Sandbox.create(); try { const clone = await sandbox.runCommand(`git clone ${repoUrl} repo`); if (clone.exitCode !== 0) { throw new Error(`Clone failed: ${clone.stderr}`); } const files: Array<{ path: string; content: string }> = []; for (const fullPath of INTERESTING_PATHS) { try { const content = await sandbox.readFile(fullPath); files.push({ path: fullPath.replace(/^repo\//, ''), content }); } catch { // file doesn't exist in this repo; skip it } } await sandbox.runCommand('cd repo && pnpm install'); const test = await sandbox.runCommand('cd repo && pnpm test'); return { sandboxId: sandbox.sandboxId, cloneExitCode: clone.exitCode, files, testResult: { exitCode: test.exitCode, stdout: test.stdout, stderr: test.stderr } }; } finally { await sandbox.stop(); } } ``` A couple of intentional choices. We're not throwing when `pnpm test` exits non-zero. Failing tests are a *finding*, not a crash. The whole point of running them is that the failures become part of the review. We're also not parsing anything yet. Parsing is the next lesson. Right now we just need to prove the tests ran and we captured the output. \*\*Warning: Troubleshooting: pnpm is not available\*\* Some Sandbox base images don't have pnpm. If `pnpm install` returns "command not found", we'll handle that in 4.3 when we detect the lockfile and pick the matching tool. For now, pick a repo that uses pnpm. \*\*Note: Troubleshooting: install takes forever\*\* `pnpm install` on a real repo can take 30-90 seconds. That's normal for a cold Sandbox. We'll speed it up with snapshots in Chapter 5. ## Try It Pick a repo that uses pnpm and has a test script (a small one — install time matters): ```bash pnpm review https://github.com/ ``` Expected output (the trailing test summary varies): ```txt Reviewing https://github.com/<...>... Sandbox: sbx_7N2k4A... Collected 2 file(s) for analysis. Overall risk: low Findings: 3 [medium] ... ... ``` You won't see the test output in the terminal yet because the CLI isn't logging it. To verify it's there, temporarily add `console.log(lifecycle.testResult)` in the CLI right after the lifecycle call. You should see something like: ```js { exitCode: 0, stdout: '> repo@1.0.0 test\n> vitest run\n\n ✓ src/sum.test.ts (3)\n...', stderr: '' } ``` Or if tests failed: ```js { exitCode: 1, stdout: '... FAIL src/sum.test.ts > adds correctly ...', stderr: '' } ``` Either way, the suite ran and we captured the result. Remove the debug log before committing. ## Commit ```bash git add src/sandbox-lifecycle.ts git commit -m "feat(sandbox): run repo test suite and capture the result" ``` ## Done-When - [ ] `pnpm install` runs in the Sandbox before tests - [ ] `pnpm test` runs after install - [ ] `testResult: { exitCode, stdout, stderr }` is returned from the lifecycle - [ ] Non-zero test exit codes don't crash the lifecycle ## Solution ```ts title="src/sandbox-lifecycle.ts" import { Sandbox } from '@vercel/sandbox'; const INTERESTING_PATHS = [ 'repo/package.json', 'repo/src/index.ts', 'repo/src/app.ts', 'repo/lib/auth.ts' ]; export type TestResult = { exitCode: number; stdout: string; stderr: string; }; export type LifecycleResult = { sandboxId: string; cloneExitCode: number; files: Array<{ path: string; content: string }>; testResult: TestResult; }; export async function runSandboxLifecycle(repoUrl: string): Promise { const sandbox = await Sandbox.create(); try { const clone = await sandbox.runCommand(`git clone ${repoUrl} repo`); if (clone.exitCode !== 0) { throw new Error(`Clone failed: ${clone.stderr}`); } const files: Array<{ path: string; content: string }> = []; for (const fullPath of INTERESTING_PATHS) { try { const content = await sandbox.readFile(fullPath); files.push({ path: fullPath.replace(/^repo\//, ''), content }); } catch { // file doesn't exist in this repo; skip it } } await sandbox.runCommand('cd repo && pnpm install'); const test = await sandbox.runCommand('cd repo && pnpm test'); return { sandboxId: sandbox.sandboxId, cloneExitCode: clone.exitCode, files, testResult: { exitCode: test.exitCode, stdout: test.stdout, stderr: test.stderr } }; } finally { await sandbox.stop(); } } ``` --- [Full course index](/academy/llms.txt) · [Sitemap](/academy/sitemap.md)