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2026-07-29 16:01
REST API

Field Masking / Sparse Fields

FilterRequestValidateMedium
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What you will learn

  • Field mask (?fields=id,name) must return ONLY those fields — extra fields leaking into response defeat the bandwidth win
  • Test invalid field names: ?fields=unknown should 400, not silently drop — dropping masks real typos in client code
  • Nested path semantics: ?fields=author.name should return { author: { name } }, not flattened to author_name

Description

Request only specific fields to reduce payload size.

Test Scenario

const response = await request.get('/api/v1/users?fields=id,name');
const body = await response.json();
expect(Object.keys(body.data[0])).toEqual(['id', 'name']);
Endpoint/api/v1/users?fields=id,name

Testing Tips

  • •Use fields query parameter
  • •Verify only requested fields returned
  • •Check nested field selection
// Playwright API Testing - REST
import { test, expect } from '@playwright/test';


test('REST API request', async ({ request }) => {
  const response = await request.get('/api/v1/resource');


  expect(response.ok()).toBeTruthy();
  expect(response.status()).toBe(200);


  const data = await response.json();
  expect(data).toBeDefined();
});

Challenge ID: rest-field-mask

2 frameworks available

API Playground

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Endpoint: /api/v1/users?fields=id,name

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