Testing Routes

In-process testing

Fastify can inject requests directly without starting a real server—ideal for unit and integration tests.

Testing with inject

Use fastify.inject() to send requests and verify responses.

import test from 'node:test';
import assert from 'node:assert';
import build from './app.js';

test('GET /health returns 200', async () => {
  const fastify = await build();
  
  const response = await fastify.inject({
    method: 'GET',
    url: '/health',
  });
  
  assert.equal(response.statusCode, 200);
  assert.deepEqual(JSON.parse(response.body), { status: 'ok' });
  
  await fastify.close();
});