VCR Plugin - Record and Replay Responses

The VCR plugins allow you to record & replay HTTP responses. It’s very useful for test purpose (using production-like predictable fixtures and avoid making actual HTTP request). You can also use it during your development cycle, when the endpoint you’re contacting is not ready yet.

Unlike the php-http/mock-client, where you have to manually define responses, the responses are automatically generated from the previously recorded ones.

Install

$ composer require --dev php-http/vcr-plugin

Usage

To record or replay a response, you will need two components, a naming strategy and a recorder.

The naming strategy

The naming strategy turn a request into a deterministic and unique identifier. The identifier must be safe to use with a filesystem. The plugin provide a default naming strategy, the PathNamingStrategy. You can define two options:

  • hash_headers: the list of header(s) that make the request unique (Ex: ‘Authorization’). The name & content of the header will be hashed to generate a unique signature. By default no header is used.
  • hash_body_methods: indicate for which request methods the body makes requests distinct. (Default: PUT, POST, PATCH)

This naming strategy will turn a GET request to https://example.org/my-path to the example.org_GET_my-path name, and optionally add hashes if the request contain a header defined in the options, or if the method is not idempotent.

To create your own strategy, you need to create a class implementing Http\Client\Plugin\Vcr\NamingStrategy\NamingStrategyInterface.

The recorder

The recorder records and replays responses. The plugin provides two recorders:

  • FilesystemRecorder: Saves the response on your filesystem using Symfony’s filesystem component and Guzzle PSR7 library.
  • InMemoryRecorder: Saves the response in memory. Response will be lost at the end of the running process

To create your own recorder, you need to create a class implementing the following interfaces:

  • Http\Client\Plugin\Vcr\Recorder\RecorderInterface used by the RecordPlugin.
  • Http\Client\Plugin\Vcr\Recorder\PlayerInterface used by the ReplayPlugin.

The plugins

There are two plugins, one to record responses, the other to replay them.

  • Http\Client\Plugin\Vcr\ReplayPlugin, use a PlayerInterface to replay previously recorded responses.
  • Http\Client\Plugin\Vcr\RecordPlugin, use a RecorderInterface instance to record the responses,

Both plugins add a response header to indicate either under which name the response has been stored (RecordPlugin, X-VCR-RECORD header), or which response name has been used to replay the request (ReplayPlugin, X-VCR-REPLAYED header).

If you plan on using both plugins at the same time (Replay or Record), the ReplayPlugin must always come first. Please also note that by default, the ReplayPlugin throws an exception when it cannot replay a request. If you want the plugin to continue the request (possibly to the actual server), set the third constructor argument to false (See example below).

Example

<?php

use Http\Client\Common\PluginClient;
use Http\Client\Plugin\Vcr\NamingStrategy\PathNamingStrategy;
use Http\Client\Plugin\Vcr\Recorder\FilesystemRecorder;
use Http\Client\Plugin\Vcr\RecordPlugin;
use Http\Client\Plugin\Vcr\ReplayPlugin;
use Http\Discovery\HttpClientDiscovery;

$namingStrategy = new PathNamingStrategy([
    'hash_headers' => ['X-Custom-Header'], // None by default
    'hash_body_methods' => ['POST'], // Default: PUT, POST, PATCH
]);
$recorder = new FilesystemRecorder('some/dir/in/vcs'); // You can use InMemoryRecorder as well

// To record responses:
$record = new RecordPlugin($namingStrategy, $recorder);

// To replay responses:
// Third argument prevent the plugin from throwing an exception when a request cannot be replayed
$replay = new ReplayPlugin($namingStrategy, $recorder, false);

$pluginClient = new PluginClient(
    HttpClientDiscovery::find(),
    [$replay, $record] // Replay should always go first
);

/** @var \Psr\Http\Message\RequestInterface $request */
$request = new MyRequest('GET', 'https://httplug.io');

// Will be recorded in "some/dir/in/vcs"
$client->sendRequest($request);

// Will be replayed from "some/dir/in/vcs"
$client->sendRequest($request);