Chapter quiz · Testing & Production

Test what you learned.

8 questions on Testing & Production. Pass 70% to clear the chapter.

Quiz

Testing & Production — Chapter Quiz

Eight questions on app.inject, supertest, Vitest, health checks and metrics, response-schema performance, Docker multi-stage builds, PM2 cluster mode, and debugging.

0/ 9

Question 1
1
What's the main advantage of app.inject() over a real HTTP request in tests?
AIt runs in-process without binding a port — faster and parallel-safeBIt bypasses validationCIt mocks the databaseDIt supports HTTP/2 only
inject routes a synthetic request through the full Fastify lifecycle without opening a socket, making tests fast and free of port conflicts.
Question 2
2
Before using supertest against app.server, you must await app.ready().
TTrueFFalse
app.ready() runs all plugin registrations and prepares the router. Without it, routes may not be wired up yet when supertest fires a request.
Question 3
3
Which Vitest command runs tests once and exits (suitable for CI)?
AvitestBvitest watchCvitest runDvitest --serve
vitest run is the one-shot CI command. Plain vitest (or vitest watch) starts watch mode.
Question 4
4
A common health-check endpoint path is /____, returning a small JSON body and 200.
/healthz (Kubernetes convention) or /health are the common liveness paths. A second /readyz covers readiness.
Question 5
5
Why does adding a response schema improve performance?
AFastify compiles a specialized JSON serializer that is much faster than JSON.stringifyBIt caches every response in memoryCIt moves serialization to a worker threadDIt enables HTTP/2 push
fast-json-stringify compiles a schema-aware serializer at startup that is roughly 2-3x faster than JSON.stringify, and it strips unknown fields as a bonus.
Question 6
6
What is the main benefit of this Dockerfile shape?
```
FROM node:20-alpine AS build
RUN npm ci && npm run build

FROM node:20-alpine
COPY --from=build /app/dist ./dist
```
AThe final image excludes dev dependencies and build toolingBIt runs as rootCIt enables HTTP/2 by defaultDIt auto-restarts on crash
The point of a multi-stage build: install dev deps and build in one layer, then ship a slim runtime image without dev deps or build tooling.
Question 7
7
What does PM2's exec_mode: 'cluster' with instances: 'max' do?
AForks one Node worker per CPU and load-balances connections across themBSpawns one process per routeCRuns the process in a Docker containerDRestarts the process every minute
PM2 cluster mode uses Node's cluster module to fork one worker per CPU and round-robins incoming connections — roughly linear speedup for stateless workloads.
Question 8
8
Which steps help you attach a debugger to a TypeScript Fastify app?
Select all that apply.
ARun with node --inspect-brk dist/index.jsBEnable sourceMap: true in tsconfig.jsonCUse tsx --inspect src/index.ts for raw TSDSet NODE_ENV=production to enable the debugger
Inspector flag, source maps, and tsx --inspect are the standard tools. NODE_ENV=production does not enable a debugger.