Mock HTTP Response Stream

4.0.2 · active · verified Tue Apr 21

Responselike provides a streamable object designed to mimic a Node.js HTTP response stream (`http.IncomingMessage`). This utility is primarily used for mocking HTTP responses in testing scenarios or for reformatting cached data to be consumed by code expecting a standard HTTP response. The current stable version is 4.0.2. The package is actively maintained by Sindre Sorhus, with releases typically occurring as needed for bug fixes or Node.js version updates, as seen with the recent v4.0.0 and v4.0.1/v4.0.2 updates. Its key differentiator is its focus on accurately replicating the streamable nature and properties of a native HTTP response, making it suitable for integrations where stream-based consumption is expected, unlike simpler object mocks.

Common errors

```
ERR_REQUIRE_ESM
```
cause Attempting to `require()` responselike in an ESM project, or attempting to `require()` a pure ESM package in a CommonJS context.

fix Use `import Response from 'responselike';` instead of `const Response = require('responselike');`. Ensure your project is set up for ESM, potentially by adding `"type": "module"` to your `package.json`.
```
TypeError: Cannot read properties of undefined (reading 'pipe')
```
cause The `body` property passed to the `Response` constructor was not a `Buffer` or was missing, leading to an unstreamable object.

fix Ensure the `body` option is explicitly set to a `Buffer.from('your content')` when creating a new `Response` instance.
```
TypeError: responselike_1.default is not a constructor
```
cause Incorrectly importing `Response` as a named export or attempting to use `new` on the module itself when it's a default export.

fix Correct the import statement to `import Response from 'responselike';` (for ESM) or verify your CommonJS wrapper if using older Node.js versions.

Warnings

breaking Version 4.0.0 and newer require Node.js version 20 or higher.
Fix: Upgrade your Node.js environment to version 20 or greater. If unable to upgrade, use `responselike@3.x` for Node.js 14+ or `responselike@2.x` for older Node.js versions.
breaking Version 3.0.0 introduced breaking changes, requiring Node.js 14 and transitioning the package to pure ESM. CommonJS `require()` is no longer supported.
Fix: Migrate your codebase to use ESM `import` statements. Refer to Sindre Sorhus's 'pure ESM' gist for guidance on migrating projects. Ensure your `package.json` is configured correctly for ESM.
breaking Since v3.0.0, the `Response` constructor now accepts a single `options` object instead of multiple positional arguments.
Fix: Refactor calls from `new Response(statusCode, headers, body, url)` to `new Response({ statusCode, headers, body, url })`.
gotcha When providing headers, keys will be automatically lowercased by the `Response` object to mimic standard HTTP header behavior.
Fix: Be aware that accessing headers should use lowercase keys, e.g., `response.headers['content-type']` even if originally provided as `{'Content-Type': '...'}`.

Install

npm install responselike npm
yarn add responselike yarn
pnpm add responselike pnpm

Imports

Response
wrong:
```
const Response = require('responselike');
```
correct:
```
import Response from 'responselike';
```
The package is pure ESM since v3.0.0, requiring `import` syntax. 'Response' is the default export.
ResponseOptions
```
import type { ResponseOptions } from 'responselike';
```
Type import for the constructor options object, useful for TypeScript users.

Quickstart

Demonstrates creating a mock HTTP response, accessing its properties, and piping its body as a stream.

import Response from 'responselike';
import { Writable } from 'stream';

class TestStream extends Writable {
  _write(chunk, encoding, callback) {
    console.log(chunk.toString());
    callback();
  }
}

const response = new Response({
	statusCode: 200,
	headers: {
		'content-type': 'text/plain',
		'x-custom-header': 'value'
	},
	body: Buffer.from('Hello, World! This is a mocked response body.'),
	url: 'https://example.com/api/data'
});

console.log(`Status Code: ${response.statusCode}`);
console.log(`URL: ${response.url}`);
console.log('Headers:', response.headers);

const testOutput = new TestStream();
console.log('\nStreaming body content:');
response.pipe(testOutput);

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