Back to Repositories

Testing Response Header Append Operations in Koa.js

This test suite validates the header append functionality in Koa’s response context, focusing on multiple header handling and array value support. The tests verify the proper behavior of appending multiple values to response headers and their interaction with the set operation.

Test Coverage Overview

The test suite provides comprehensive coverage of the ctx.append() functionality for HTTP headers:

Multiple header value appending
Array-based header value handling
Interaction between append and set operations
Header value reset scenarios

Implementation Analysis

The testing approach utilizes Node’s native test framework with describe/it blocks for structured test organization. The implementation follows a context-based pattern where each test case creates a fresh context object, enabling isolated header manipulation testing.

The tests leverage Node’s assert module for verification, particularly using deepStrictEqual for array comparisons.

Technical Details

Testing infrastructure includes:

Node.js native test framework
Custom context helper utilities
Assert module for assertions
Strict mode JavaScript execution

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test contexts for each case
Comprehensive edge case coverage
Clear test case descriptions
Consistent assertion patterns
Proper setup and teardown handling

koajs/koa

__tests__/response/append.test.js

            
'use strict'

const { describe, it } = require('node:test')
const assert = require('assert')
const context = require('../../test-helpers/context')

describe('ctx.append(name, val)', () => {
  it('should append multiple headers', () => {
    const ctx = context()
    ctx.append('x-foo', 'bar1')
    ctx.append('x-foo', 'bar2')
    assert.deepStrictEqual(ctx.response.header['x-foo'], ['bar1', 'bar2'])
  })

  it('should accept array of values', () => {
    const ctx = context()

    ctx.append('Set-Cookie', ['foo=bar', 'fizz=buzz'])
    ctx.append('Set-Cookie', 'hi=again')
    assert.deepStrictEqual(ctx.response.header['set-cookie'], ['foo=bar', 'fizz=buzz', 'hi=again'])
  })

  it('should get reset by res.set(field, val)', () => {
    const ctx = context()

    ctx.append('Link', '<http://localhost/>')
    ctx.append('Link', '<http://localhost:80/>')

    ctx.set('Link', '<http://127.0.0.1/>')

    assert.strictEqual(ctx.response.header.link, '<http://127.0.0.1/>')
  })

  it('should work with res.set(field, val) first', () => {
    const ctx = context()

    ctx.set('Link', '<http://localhost/>')
    ctx.append('Link', '<http://localhost:80/>')

    assert.deepStrictEqual(ctx.response.header.link, ['<http://localhost/>', '<http://localhost:80/>'])
  })
})