diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..be8e9d2
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,41 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  tests:
+    name: PHP ${{ matrix.php }} (${{ matrix.dependencies }} dependencies)
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        # highest: Symfony 7.4 on PHP 8.2/8.3, Symfony 8 on PHP 8.4+
+        php: ['8.2', '8.3', '8.4', '8.5']
+        dependencies: [highest]
+        include:
+          # lowest: Symfony 6.4, PSR-7 v1.1, guzzlehttp/psr7 v2
+          - php: '8.2'
+            dependencies: lowest
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          coverage: none
+
+      - run: composer validate --strict --no-check-lock
+
+      - uses: ramsey/composer-install@v3
+        with:
+          dependency-versions: ${{ matrix.dependencies }}
+
+      - run: vendor/bin/phpunit
diff --git a/.gitignore b/.gitignore
index bd8dd6a..4b45471 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,3 +14,4 @@ composer.lock
 
 # PHPUnit cache
 .phpunit.result.cache
+.phpunit.cache/
diff --git a/.openapi-generator-ignore b/.openapi-generator-ignore
index 7484ee5..81cb411 100644
--- a/.openapi-generator-ignore
+++ b/.openapi-generator-ignore
@@ -21,3 +21,11 @@
 #docs/*.md
 # Then explicitly reverse the ignore rule for a single file:
 #!docs/README.md
+
+# Hand-maintained files: keep them when regenerating the SDK
+.gitignore
+.php-cs-fixer.dist.php
+.travis.yml
+README.md
+composer.json
+phpunit.xml.dist
diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index af9cf39..ea83b73 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -12,7 +12,9 @@
 ;
 
 $config = new PhpCsFixer\Config();
-return $config->setRules([
+return $config
+    ->setRiskyAllowed(true)
+    ->setRules([
         '@PSR12' => true,
         'phpdoc_order' => true,
         'array_syntax' => [ 'syntax' => 'short' ],
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 667b815..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,8 +0,0 @@
-language: php
-# Bionic environment has preinstalled PHP from 7.1 to 7.4
-# https://docs.travis-ci.com/user/reference/bionic/#php-support
-dist: bionic
-php:
-    - 7.4
-before_install: "composer install"
-script: "vendor/bin/phpunit"
diff --git a/README.md b/README.md
index 2d7715d..3dbe1da 100644
--- a/README.md
+++ b/README.md
@@ -1,13 +1,15 @@
-# OpenAPIClient-php
+# eConnect PSB PHP SDK
 
-PHP SDK for econnect PSB (https://psb.econnect.eu/?urls.primaryName=V1)
+PHP SDK for the eConnect Procurement Service Bus (PSB) API (https://psb.econnect.eu/?urls.primaryName=V1)
 
 
 ## Installation & Usage
 
 ### Requirements
 
-PHP 8.2 and later.
+- PHP 8.2 or later
+- A [PSR-18](https://packagist.org/providers/psr/http-client-implementation) HTTP client with an [HTTPlug async](https://packagist.org/providers/php-http/async-client-implementation) implementation, such as Symfony HttpClient or Guzzle
+- Compatible with Symfony 6.4, 7.x and 8.x (Symfony 8 itself requires PHP 8.4 or later)
 
 ### Composer
 
@@ -22,23 +24,23 @@ To install the bindings via [Composer](https://getcomposer.org/), add the follow
     }
   ],
   "require": {
-    "QbilSoftware/econnect-psb-php": "@dev-main"
+    "qbil-software/econnect-psb-php": "dev-main"
   }
 }
 ```
 
-Then run `composer install`
+Then run `composer install`.
 
-Your project is free to choose the http client of your choice
-Please require packages that will provide http client functionality:
-https://packagist.org/providers/psr/http-client-implementation
-https://packagist.org/providers/php-http/async-client-implementation
-https://packagist.org/providers/psr/http-factory-implementation
+Your project is free to choose the HTTP client of your choice. In a Symfony application, use Symfony HttpClient:
 
-As an example:
+```
+composer require symfony/http-client guzzlehttp/promises
+```
+
+Or use Guzzle 7 with its HTTPlug adapter:
 
 ```
-composer require guzzlehttp/guzzle php-http/guzzle7-adapter http-interop/http-factory-guzzle
+composer require guzzlehttp/guzzle php-http/guzzle7-adapter
 ```
 
 ### Manual Installation
@@ -47,7 +49,7 @@ Download the files and include `autoload.php`:
 
 ```php
 <?php
-require_once('/path/to/OpenAPIClient-php/vendor/autoload.php');
+require_once('/path/to/econnect-psb-php/vendor/autoload.php');
 ```
 
 ## Getting Started
@@ -58,47 +60,66 @@ Please follow the [installation procedure](#installation--usage) and then run th
 <?php
 require_once(__DIR__ . '/vendor/autoload.php');
 
-
-
-// Configure API key authorization: Subscription-Key
-$config = EConnect\Psb\Configuration::getDefaultConfiguration()->setApiKey('Subscription-Key', 'YOUR_API_KEY');
-// Uncomment below to setup prefix (e.g. Bearer) for API key, if needed
-// $config = EConnect\Psb\Configuration::getDefaultConfiguration()->setApiKeyPrefix('Subscription-Key', 'Bearer');
-
-$config
-    ->setUsername("{username}")
-    ->setPassword("{password}");
-    ->setHost("https://psb.econnect.eu")
+$config = (new EConnect\Psb\Configuration())
+    ->setHost('https://psb.econnect.eu')
+    ->setUsername('{username}')
+    ->setPassword('{password}')
     ->setApiKey('Subscription-Key', '{subscription key}');
-    
-$authN = new \EConnect\Psb\OidcAuthenticator(
-    \Http\Discovery\Psr18ClientDiscovery::find(),
-    \Http\Discovery\Psr17FactoryDiscovery::findRequestFactory(),
-    \Http\Discovery\Psr17FactoryDiscovery::findStreamFactory(),
-    new \Symfony\Component\Clock\NativeClock(),
+
+$authenticator = new EConnect\Psb\OidcAuthenticator(
+    Http\Discovery\Psr18ClientDiscovery::find(),
+    Http\Discovery\Psr17FactoryDiscovery::findRequestFactory(),
+    Http\Discovery\Psr17FactoryDiscovery::findStreamFactory(),
+    new Symfony\Component\Clock\NativeClock(),
     $config,
 );
-$authN->login('{clientId}', '{clientSecret}');
 
-$apiInstance = new EConnect\Psb\Api\HookApi(
-    // If you want use custom http client, pass your client which implements `Psr\Http\Client\ClientInterface`.
-    // This is optional, `Psr18ClientDiscovery` will be used to find http client. For instance `GuzzleHttp\Client` implements that interface
-    \Http\Discovery\Psr18ClientDiscovery::find(),
-    $config
-);
+// Fetches an access token and stores it in $config. The token is cached and renewed
+// shortly before it expires, so it is cheap to call this before every batch of API calls.
+$authenticator->authenticate('{clientId}', '{clientSecret}');
+
+// The HTTP client is optional: when omitted, it is discovered with `Psr18ClientDiscovery`.
+$apiInstance = new EConnect\Psb\Api\HookApi(null, $config);
 
 try {
     $result = $apiInstance->getHookConfigs();
     print_r($result);
-} catch (Exception $e) {
+} catch (EConnect\Psb\ApiException $e) {
     echo 'Exception when calling HookApi->getHookConfigs: ', $e->getMessage(), PHP_EOL;
 }
+```
 
+### Symfony
+
+With `symfony/framework-bundle` and `symfony/http-client` installed, register the SDK as services, for example in `config/services.yaml`:
+
+```yaml
+services:
+    EConnect\Psb\Configuration:
+        calls:
+            - setHost: ['%env(PSB_HOST)%']
+            - setUsername: ['%env(PSB_USERNAME)%']
+            - setPassword: ['%env(PSB_PASSWORD)%']
+            - setApiKey: ['Subscription-Key', '%env(PSB_SUBSCRIPTION_KEY)%']
+
+    EConnect\Psb\OidcAuthenticator:
+        arguments:
+            $httpClient: '@psr18.http_client'
+            $requestFactory: '@psr18.http_client'
+            $streamFactory: '@psr18.http_client'
+            $clock: '@clock'
+            $config: '@EConnect\Psb\Configuration'
+
+    EConnect\Psb\Api\:
+        resource: '%kernel.project_dir%/vendor/qbil-software/econnect-psb-php/lib/Api/'
+        autowire: true
 ```
 
+The API classes then use Symfony HttpClient for both synchronous and asynchronous requests. Inject `OidcAuthenticator` and the API classes you need into your own services, and call `authenticate()` before using the APIs.
+
 ## API Endpoints
 
-All URIs are relative to *http://localhost*
+All URIs are relative to the configured host, e.g. *https://psb.econnect.eu*
 
 Class | Method | HTTP request | Description
 ------------ | ------------- | ------------- | -------------
@@ -112,6 +133,13 @@ Class | Method | HTTP request | Description
 *MeApi* | [**getUser**](docs/Api/MeApi.md#getuser) | **GET** /api/v1/me | Get user.
 *MeApi* | [**getUserParty**](docs/Api/MeApi.md#getuserparty) | **GET** /api/v1/me/party | Get parties.
 *PeppolApi* | [**getDeliveryOptions**](docs/Api/PeppolApi.md#getdeliveryoptions) | **GET** /api/v1/peppol/deliveryOption | Advanced recipient party lookup in Peppol.
+*PeppolApi* | [**getPeppolConfig**](lib/Api/PeppolApi.php) | **GET** /api/v1/peppol/config | Get default Peppol configuration
+*PeppolApi* | [**getPeppolParties**](lib/Api/PeppolApi.php) | **GET** /api/v1/peppol/config/party | Get your Peppol participants
+*PeppolApi* | [**getPeppolPartyConfig**](lib/Api/PeppolApi.php) | **GET** /api/v1/peppol/config/party/{partyId} | Get participant Peppol configuration
+*PeppolApi* | [**removePeppolPartyConfig**](lib/Api/PeppolApi.php) | **DELETE** /api/v1/peppol/config/party/{partyId} | Un register (Remove) participant in Peppol
+*PeppolApi* | [**requestPartyPrepareToMigrate**](lib/Api/PeppolApi.php) | **GET** /api/v1/peppol/{partyId}/prepareToMigrate | Generates a migration key and registers it with the SML to enable participant transfer between SMPs
+*PeppolApi* | [**setPeppolConfig**](lib/Api/PeppolApi.php) | **PUT** /api/v1/peppol/config | Add or update default Peppol configuration
+*PeppolApi* | [**setPeppolPartyConfig**](lib/Api/PeppolApi.php) | **PUT** /api/v1/peppol/config/party/{partyId} | Register or update participant in Peppol
 *PurchaseInvoiceApi* | [**deletePurchaseInvoice**](docs/Api/PurchaseInvoiceApi.md#deletepurchaseinvoice) | **DELETE** /api/v1/{partyId}/purchaseInvoice/{documentId} | Delete purchase invoice.
 *PurchaseInvoiceApi* | [**downloadPurchaseInvoice**](docs/Api/PurchaseInvoiceApi.md#downloadpurchaseinvoice) | **GET** /api/v1/{partyId}/purchaseInvoice/{documentId}/download | Download purchase invoice.
 *PurchaseInvoiceApi* | [**getPurchaseInvoiceStatuses**](docs/Api/PurchaseInvoiceApi.md#getpurchaseinvoicestatuses) | **GET** /api/v1/{partyId}/purchaseInvoice/{documentId}/status | Get purchase invoice statuses (FOR DEBUGGING ONLY).
@@ -140,6 +168,7 @@ Class | Method | HTTP request | Description
 
 ## Models
 
+- [BusinessCardProperty](lib/Model/BusinessCardProperty.php)
 - [DeliveryOption](docs/Model/DeliveryOption.md)
 - [Document](docs/Model/Document.md)
 - [DocumentFamily](docs/Model/DocumentFamily.md)
@@ -157,7 +186,12 @@ Class | Method | HTTP request | Description
 - [Party](docs/Model/Party.md)
 - [PartyPagedResult](docs/Model/PartyPagedResult.md)
 - [PartyPermissions](docs/Model/PartyPermissions.md)
+- [PeppolBusinessCard](lib/Model/PeppolBusinessCard.php)
+- [PeppolCapability](lib/Model/PeppolCapability.php)
+- [PeppolConfig](lib/Model/PeppolConfig.php)
 - [PeppolMigrateConfig](docs/Model/PeppolMigrateConfig.md)
+- [PeppolPartyConfig](lib/Model/PeppolPartyConfig.php)
+- [PeppolPartyVerification](lib/Model/PeppolPartyVerification.php)
 - [PrepareToMigrateResponse](docs/Model/PrepareToMigrateResponse.md)
 - [ProcessId](docs/Model/ProcessId.md)
 - [TransportProtocol](docs/Model/TransportProtocol.md)
@@ -189,9 +223,21 @@ To run the tests, use:
 
 ```bash
 composer install
-vendor/bin/phpunit
+composer test
 ```
 
+The `unit` test suite in `test/Unit` covers authentication, (de)serialization and request building, including a run on top of Symfony HttpClient. The `generated` suite in `test/Api` and `test/Model` contains the placeholders created by OpenAPI Generator.
+
+## Regenerating the SDK
+
+Hand-maintained files are listed in `.openapi-generator-ignore` and are kept when regenerating. The generated code also carries the following patches, which have to be re-applied after regenerating:
+
+- `lib/Api/*.php`: `createRequest()` always builds the request through the PSR-17 factories, and multipart requests set `Content-Type: multipart/form-data; boundary=...` from the `MultipartStream`.
+- `lib/ObjectSerializer.php`: dates are detected with `\DateTimeInterface`, so `\DateTimeImmutable` values are serialized as well.
+- `lib/DebugPlugin.php`: failed requests are logged as `<METHOD path HTTP/version> code message`.
+
+`lib/functions.php` provides `GuzzleHttp\Psr7\try_fopen()`, which the generated file uploads call but `guzzlehttp/psr7` 2.0 and later no longer ship.
+
 ## Author
 
 techsupport@econnect.eu
diff --git a/composer.json b/composer.json
index 9708515..f6c2728 100644
--- a/composer.json
+++ b/composer.json
@@ -1,18 +1,26 @@
 {
     "name": "qbil-software/econnect-psb-php",
-    "description": "No description provided (generated by Openapi Generator https://github.com/openapitools/openapi-generator)",
+    "description": "PHP SDK for the eConnect Procurement Service Bus (PSB) API",
+    "type": "library",
     "keywords": [
-        "openapitools",
-        "openapi-generator",
+        "econnect",
+        "psb",
+        "peppol",
+        "e-invoicing",
         "openapi",
         "php",
         "sdk",
         "rest",
-        "api"
+        "api",
+        "symfony"
     ],
-    "homepage": "https://openapi-generator.tech",
-    "license": "unlicense",
+    "homepage": "https://github.com/QbilSoftware/econnect-psb-php",
+    "license": "MIT",
     "authors": [
+        {
+            "name": "Qbil Software",
+            "homepage": "https://www.qbilsoftware.com"
+        },
         {
             "name": "OpenAPI-Generator contributors",
             "homepage": "https://openapi-generator.tech"
@@ -26,25 +34,27 @@
     },
     "require": {
         "php": "^8.2",
-        "ext-curl": "*",
         "ext-json": "*",
         "ext-mbstring": "*",
-        "guzzlehttp/psr7": "^1.8 || ^2.0",
+        "guzzlehttp/psr7": "^2.12.3 || ^3.0",
         "php-http/async-client-implementation": "^1.0",
         "php-http/client-common": "^2.4",
-        "php-http/discovery": "^1.14",
+        "php-http/discovery": "^1.15",
         "php-http/httplug": "^2.2",
+        "psr/clock": "^1.0",
+        "psr/http-client": "^1.0",
         "psr/http-client-implementation": "^1.0",
         "psr/http-factory": "^1.0",
         "psr/http-factory-implementation": "^1.0",
-        "psr/http-message": "^1.0",
-        "symfony/clock": "^7.2"
+        "psr/http-message": "^1.1 || ^2.0",
+        "symfony/clock": "^6.4 || ^7.0 || ^8.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^8.0 || ^9.0",
-        "friendsofphp/php-cs-fixer": "^v3.7",
-        "guzzlehttp/guzzle": "^7.0",
-        "php-http/guzzle7-adapter": "^1.0"
+        "friendsofphp/php-cs-fixer": "^3.7",
+        "guzzlehttp/promises": "^2.0 || ^3.0",
+        "php-http/mock-client": "^1.6",
+        "phpunit/phpunit": "^11.5 || ^12.0 || ^13.0",
+        "symfony/http-client": "^6.4 || ^7.0 || ^8.0"
     },
     "autoload": {
         "psr-4": { "EConnect\\Psb\\" : "lib/" },
@@ -52,5 +62,10 @@
     },
     "autoload-dev": {
         "psr-4": { "EConnect\\Psb\\Test\\" : "test/" }
+    },
+    "scripts": {
+        "test": "phpunit",
+        "cs-check": "php-cs-fixer fix --dry-run --diff",
+        "cs-fix": "php-cs-fixer fix"
     }
 }
diff --git a/lib/DebugPlugin.php b/lib/DebugPlugin.php
index feae8ba..f764379 100644
--- a/lib/DebugPlugin.php
+++ b/lib/DebugPlugin.php
@@ -97,7 +97,7 @@ private function logError(RequestInterface $request, ClientExceptionInterface $e
         $protocol = $request->getProtocolVersion();
         $error = $exception->getMessage();
         $responseCode = $exception->getCode();
-        \fprintf($this->output, '<%s HTTP/%s> %s %s', $methodAndPath, $responseCode, $error, $protocol);
+        \fprintf($this->output, '<%s HTTP/%s> %s %s', $methodAndPath, $protocol, $responseCode, $error);
         \fwrite($this->output, "\n");
     }
 }
\ No newline at end of file
diff --git a/lib/ObjectSerializer.php b/lib/ObjectSerializer.php
index acaa53a..3edadc4 100644
--- a/lib/ObjectSerializer.php
+++ b/lib/ObjectSerializer.php
@@ -71,7 +71,7 @@ public static function sanitizeForSerialization($data, $type = null, $format = n
             return $data;
         }
 
-        if ($data instanceof \DateTime) {
+        if ($data instanceof \DateTimeInterface) {
             return ($format === 'date') ? $data->format('Y-m-d') : $data->format(self::$dateTimeFormat);
         }
 
@@ -243,7 +243,7 @@ public static function toQueryValue(
         }
 
         # Handle DateTime objects in query
-        if ($openApiType === "\\DateTime" && $value instanceof \DateTime) {
+        if ($openApiType === "\\DateTime" && $value instanceof \DateTimeInterface) {
             return ["{$paramName}" => $value->format(self::$dateTimeFormat)];
         }
 
@@ -353,13 +353,13 @@ public static function toFormValue($value)
      * If it's a datetime object, format it in ISO8601
      * If it's a boolean, convert it to "true" or "false".
      *
-     * @param float|int|bool|\DateTime $value the value of the parameter
+     * @param float|int|bool|\DateTimeInterface $value the value of the parameter
      *
      * @return string the header string
      */
     public static function toString($value)
     {
-        if ($value instanceof \DateTime) { // datetime in ISO8601 format
+        if ($value instanceof \DateTimeInterface) { // datetime in ISO8601 format
             return $value->format(self::$dateTimeFormat);
         } elseif (is_bool($value)) {
             return $value ? 'true' : 'false';
diff --git a/lib/OidcAuthenticator.php b/lib/OidcAuthenticator.php
index f80de4d..98f7f53 100644
--- a/lib/OidcAuthenticator.php
+++ b/lib/OidcAuthenticator.php
@@ -5,12 +5,21 @@
 namespace EConnect\Psb;
 
 use Psr\Clock\ClockInterface;
+use Psr\Http\Client\ClientExceptionInterface;
 use Psr\Http\Client\ClientInterface;
 use Psr\Http\Message\RequestFactoryInterface;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\StreamFactoryInterface;
 
 class OidcAuthenticator
 {
+    /**
+     * Seconds before the reported expiry at which a token is renewed, so that
+     * requests in flight don't reach the API with an expired token.
+     */
+    private const EXPIRY_LEEWAY = 60;
+
     private \DateTimeImmutable $validUntil;
 
     public function __construct(
@@ -27,7 +36,7 @@ public function authenticate(string $clientId, string $clientSecret): string
             return $this->config->getAccessToken();
         }
 
-        $identityUrl = str_replace('psb', 'identity', $this->config->getHost());
+        $identityUrl = rtrim(str_replace('psb', 'identity', $this->config->getHost()), '/');
         $discoveryUrl = "{$identityUrl}/.well-known/openid-configuration";
 
         // 1. Fetch OpenID Configuration
@@ -35,12 +44,12 @@ public function authenticate(string $clientId, string $clientSecret): string
             ->requestFactory
             ->createRequest('GET', $discoveryUrl);
 
-        $discoveryResponse = $this->httpClient->sendRequest($discoveryRequest);
-        $metadata = json_decode((string) $discoveryResponse->getBody(), true, 512, JSON_THROW_ON_ERROR);
+        $discoveryResponse = $this->send($discoveryRequest);
+        $metadata = $this->decode($discoveryRequest, $discoveryResponse, 'OpenID discovery failed');
 
         $tokenEndpoint = $metadata['token_endpoint'] ?? null;
 
-        if (!$tokenEndpoint) {
+        if (!is_string($tokenEndpoint) || $tokenEndpoint === '') {
             throw new ApiException(
                 'Missing token_endpoint in OpenID configuration.',
                 $discoveryRequest,
@@ -64,10 +73,10 @@ public function authenticate(string $clientId, string $clientSecret): string
             ->withHeader('Content-Type', 'application/x-www-form-urlencoded')
             ->withBody($this->streamFactory->createStream($formBody));
 
-        $tokenResponse = $this->httpClient->sendRequest($tokenRequest);
-        $tokenData = json_decode((string) $tokenResponse->getBody(), true, 512, JSON_THROW_ON_ERROR);
+        $tokenResponse = $this->send($tokenRequest);
+        $tokenData = $this->decode($tokenRequest, $tokenResponse, 'OIDC login failed');
 
-        if (empty($tokenData['access_token']) || empty($tokenData['expires_in'])) {
+        if (empty($tokenData['access_token']) || !is_string($tokenData['access_token']) || !is_numeric($tokenData['expires_in'] ?? null)) {
             throw new ApiException(
                 'OIDC login failed: missing access token or expiry.',
                 $tokenRequest,
@@ -76,9 +85,45 @@ public function authenticate(string $clientId, string $clientSecret): string
         }
 
         // 3. Store token
-        $this->validUntil = $this->clock->now()->add(new \DateInterval("PT{$tokenData['expires_in']}S"));
+        $lifetime = max(0, (int) $tokenData['expires_in'] - self::EXPIRY_LEEWAY);
+        $this->validUntil = $this->clock->now()->add(new \DateInterval("PT{$lifetime}S"));
         $this->config->setAccessToken($tokenData['access_token']);
 
         return $this->config->getAccessToken();
     }
+
+    private function send(RequestInterface $request): ResponseInterface
+    {
+        try {
+            return $this->httpClient->sendRequest($request);
+        } catch (ClientExceptionInterface $e) {
+            throw new ApiException("[{$e->getCode()}] {$e->getMessage()}", $request, null, $e);
+        }
+    }
+
+    /**
+     * @return array<mixed>
+     */
+    private function decode(RequestInterface $request, ResponseInterface $response, string $error): array
+    {
+        $statusCode = $response->getStatusCode();
+        $data = json_decode((string) $response->getBody(), true);
+
+        if ($statusCode < 200 || $statusCode > 299) {
+            // OAuth 2.0 error responses describe the failure in `error_description` / `error` (RFC 6749, section 5.2)
+            $reason = $data['error_description'] ?? $data['error'] ?? null;
+
+            throw new ApiException(
+                sprintf('%s: [%d] %s', $error, $statusCode, is_string($reason) ? $reason : $response->getReasonPhrase()),
+                $request,
+                $response
+            );
+        }
+
+        if (!is_array($data)) {
+            throw new ApiException("{$error}: response is not a JSON object.", $request, $response);
+        }
+
+        return $data;
+    }
 }
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 485899a..5d2f969 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,18 +1,31 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" bootstrap="./vendor/autoload.php" colors="true" convertErrorsToExceptions="true" convertNoticesToExceptions="true" convertWarningsToExceptions="true" stopOnFailure="false" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
-  <coverage processUncoveredFiles="true">
-    <include>
-      <directory suffix=".php">./lib/Api</directory>
-      <directory suffix=".php">./lib/Model</directory>
-    </include>
-  </coverage>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         cacheDirectory=".phpunit.cache"
+         colors="true"
+         failOnDeprecation="true"
+         failOnNotice="true"
+         failOnWarning="true"
+         displayDetailsOnTestsThatTriggerDeprecations="true"
+         displayDetailsOnTestsThatTriggerNotices="true"
+         displayDetailsOnTestsThatTriggerWarnings="true"
+         displayDetailsOnTestsThatTriggerErrors="true">
   <testsuites>
-    <testsuite name="tests">
+    <testsuite name="unit">
+      <directory>./test/Unit</directory>
+    </testsuite>
+    <testsuite name="generated">
       <directory>./test/Api</directory>
       <directory>./test/Model</directory>
     </testsuite>
   </testsuites>
+  <source>
+    <include>
+      <directory suffix=".php">./lib</directory>
+    </include>
+  </source>
   <php>
-    <ini name="error_reporting" value="E_ALL"/>
+    <ini name="error_reporting" value="-1"/>
   </php>
 </phpunit>
diff --git a/test/Unit/ApiClientTest.php b/test/Unit/ApiClientTest.php
new file mode 100644
index 0000000..195d3f8
--- /dev/null
+++ b/test/Unit/ApiClientTest.php
@@ -0,0 +1,146 @@
+<?php
+
+declare(strict_types=1);
+
+namespace EConnect\Psb\Test\Unit;
+
+use EConnect\Psb\Api\HookApi;
+use EConnect\Psb\Api\SalesInvoiceApi;
+use EConnect\Psb\ApiException;
+use EConnect\Psb\Configuration;
+use EConnect\Psb\Model\Document;
+use EConnect\Psb\Model\Hook;
+use GuzzleHttp\Psr7\HttpFactory;
+use GuzzleHttp\Psr7\Response;
+use Http\Mock\Client;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Exercises the generated API classes end-to-end against a mocked HTTP client.
+ */
+final class ApiClientTest extends TestCase
+{
+    private Client $client;
+    private Configuration $config;
+
+    protected function setUp(): void
+    {
+        $this->client = new Client();
+        $this->config = (new Configuration())
+            ->setHost('https://psb.example.test')
+            ->setApiKey('Subscription-Key', 'subscription-key')
+            ->setAccessToken('access-token');
+    }
+
+    public function testRequestCarriesAuthenticationAndDeserializesResponse(): void
+    {
+        $this->client->addResponse($this->jsonResponse(200, [[
+            'id' => 'hook-1',
+            'name' => 'Default',
+            'action' => 'https://example.test/hook',
+            'createdOn' => '2026-01-02T03:04:05+00:00',
+        ]]));
+
+        $hooks = $this->createApi(HookApi::class)->getHookConfigs();
+
+        self::assertCount(1, $hooks);
+        self::assertInstanceOf(Hook::class, $hooks[0]);
+        self::assertSame('hook-1', $hooks[0]->getId());
+
+        $request = $this->client->getLastRequest();
+        self::assertSame('GET', $request->getMethod());
+        self::assertSame('https://psb.example.test/api/v1/hook', (string) $request->getUri());
+        self::assertSame('subscription-key', $request->getHeaderLine('Subscription-Key'));
+        self::assertSame('Bearer access-token', $request->getHeaderLine('Authorization'));
+        self::assertSame('application/json', $request->getHeaderLine('Accept'));
+    }
+
+    public function testPathParametersAreEncodedAndBodyIsSerialized(): void
+    {
+        $this->client->addResponse($this->jsonResponse(200, [
+            'id' => 'hook-1',
+            'name' => 'Default',
+            'action' => 'https://example.test/hook',
+        ]));
+
+        $hook = (new Hook())
+            ->setId('hook-1')
+            ->setName('Default')
+            ->setAction('https://example.test/hook')
+            ->setCreatedOn(new \DateTimeImmutable('2026-01-02T03:04:05+00:00'));
+
+        $this->createApi(HookApi::class)->subscribe('NL:KVK:12345678', $hook);
+
+        $request = $this->client->getLastRequest();
+        self::assertSame('PUT', $request->getMethod());
+        self::assertSame('/api/v1/NL%3AKVK%3A12345678/hook', $request->getUri()->getPath());
+        self::assertSame('application/json', $request->getHeaderLine('Content-Type'));
+        self::assertSame([
+            'id' => 'hook-1',
+            'name' => 'Default',
+            'action' => 'https://example.test/hook',
+            'createdOn' => '2026-01-02T03:04:05+00:00',
+        ], json_decode((string) $request->getBody(), true, 512, JSON_THROW_ON_ERROR));
+    }
+
+    public function testFileUploadSendsMultipartBodyWithBoundary(): void
+    {
+        $this->client->addResponse($this->jsonResponse(200, ['id' => 'document-1']));
+
+        $file = tempnam(sys_get_temp_dir(), 'psb');
+        file_put_contents($file, '<Invoice>UBL</Invoice>');
+
+        try {
+            $document = $this->createApi(SalesInvoiceApi::class)->sendSalesInvoice('NL:KVK:12345678', new \SplFileObject($file), null, 'peppol');
+        } finally {
+            unlink($file);
+        }
+
+        self::assertInstanceOf(Document::class, $document);
+        self::assertSame('document-1', $document->getId());
+
+        $request = $this->client->getLastRequest();
+        self::assertSame('POST', $request->getMethod());
+        self::assertSame('channel=peppol', $request->getUri()->getQuery());
+        self::assertMatchesRegularExpression('~^multipart/form-data; boundary=(\S+)$~', $request->getHeaderLine('Content-Type'));
+
+        $boundary = substr($request->getHeaderLine('Content-Type'), strlen('multipart/form-data; boundary='));
+        $body = (string) $request->getBody();
+        self::assertStringStartsWith("--{$boundary}\r\n", $body);
+        self::assertStringContainsString('Content-Disposition: form-data; name="file"; filename="' . basename($file) . '"', $body);
+        self::assertStringContainsString('<Invoice>UBL</Invoice>', $body);
+    }
+
+    public function testErrorResponsesAreConvertedToApiException(): void
+    {
+        $this->client->addResponse($this->jsonResponse(404, ['title' => 'Not Found']));
+
+        try {
+            $this->createApi(HookApi::class)->getHookConfigs();
+            self::fail('Expected an ApiException');
+        } catch (ApiException $e) {
+            self::assertSame(404, $e->getCode());
+            self::assertSame('[404] Error connecting to the API (https://psb.example.test/api/v1/hook)', $e->getMessage());
+            self::assertSame('{"title":"Not Found"}', $e->getResponseBody());
+        }
+    }
+
+    /**
+     * @template T of object
+     *
+     * @param class-string<T> $class
+     *
+     * @return T
+     */
+    private function createApi(string $class): object
+    {
+        $factory = new HttpFactory();
+
+        return new $class($this->client, $this->config, $this->client, $factory, $factory, $factory);
+    }
+
+    private function jsonResponse(int $status, mixed $body): Response
+    {
+        return new Response($status, ['Content-Type' => 'application/json'], json_encode($body, JSON_THROW_ON_ERROR));
+    }
+}
diff --git a/test/Unit/DebugPluginTest.php b/test/Unit/DebugPluginTest.php
new file mode 100644
index 0000000..b8dd365
--- /dev/null
+++ b/test/Unit/DebugPluginTest.php
@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+namespace EConnect\Psb\Test\Unit;
+
+use EConnect\Psb\DebugPlugin;
+use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\Psr7\Response;
+use Http\Client\Exception\NetworkException;
+use Http\Client\Promise\HttpFulfilledPromise;
+use Http\Client\Promise\HttpRejectedPromise;
+use PHPUnit\Framework\TestCase;
+
+final class DebugPluginTest extends TestCase
+{
+    /** @var resource */
+    private $output;
+
+    protected function setUp(): void
+    {
+        $this->output = fopen('php://memory', 'w+b');
+    }
+
+    protected function tearDown(): void
+    {
+        fclose($this->output);
+    }
+
+    public function testLogsSuccessfulResponses(): void
+    {
+        $request = new Request('GET', 'https://psb.example.test/api/v1/me');
+
+        (new DebugPlugin($this->output))
+            ->handleRequest($request, static fn () => new HttpFulfilledPromise(new Response(200)), static fn () => null)
+            ->wait();
+
+        self::assertSame("<GET /api/v1/me HTTP/1.1> 200\n", $this->readOutput());
+    }
+
+    public function testLogsFailedRequests(): void
+    {
+        $request = new Request('GET', 'https://psb.example.test/api/v1/me');
+        $exception = new NetworkException('Connection refused', $request);
+
+        $promise = (new DebugPlugin($this->output))
+            ->handleRequest($request, static fn () => new HttpRejectedPromise($exception), static fn () => null);
+
+        try {
+            $promise->wait();
+            self::fail('Expected the exception to be rethrown');
+        } catch (NetworkException $e) {
+            self::assertSame($exception, $e);
+        }
+
+        self::assertSame("<GET /api/v1/me HTTP/1.1> 0 Connection refused\n", $this->readOutput());
+    }
+
+    private function readOutput(): string
+    {
+        rewind($this->output);
+
+        return stream_get_contents($this->output);
+    }
+}
diff --git a/test/Unit/ObjectSerializerTest.php b/test/Unit/ObjectSerializerTest.php
new file mode 100644
index 0000000..c4a221f
--- /dev/null
+++ b/test/Unit/ObjectSerializerTest.php
@@ -0,0 +1,76 @@
+<?php
+
+declare(strict_types=1);
+
+namespace EConnect\Psb\Test\Unit;
+
+use EConnect\Psb\Model\Hook;
+use EConnect\Psb\ObjectSerializer;
+use PHPUnit\Framework\TestCase;
+
+final class ObjectSerializerTest extends TestCase
+{
+    public function testSanitizeForSerializationFormatsImmutableDates(): void
+    {
+        $hook = (new Hook())
+            ->setId('hook-1')
+            ->setName('Default')
+            ->setAction('https://example.test/hook')
+            ->setCreatedOn(new \DateTimeImmutable('2026-01-02T03:04:05+00:00'));
+
+        $serialized = ObjectSerializer::sanitizeForSerialization($hook);
+
+        self::assertSame('2026-01-02T03:04:05+00:00', $serialized->createdOn);
+    }
+
+    public function testDateTimeValuesAreFormattedForQueryAndPath(): void
+    {
+        $date = new \DateTimeImmutable('2026-01-02T03:04:05+00:00');
+
+        self::assertSame(['since' => '2026-01-02T03:04:05+00:00'], ObjectSerializer::toQueryValue($date, 'since', '\DateTime'));
+        self::assertSame('2026-01-02T03%3A04%3A05%2B00%3A00', ObjectSerializer::toPathValue($date));
+    }
+
+    public function testDeserializeHydratesModelsFromJson(): void
+    {
+        $json = json_encode([[
+            'id' => 'hook-1',
+            'name' => 'Default',
+            'action' => 'https://example.test/hook',
+            'topics' => ['invoice-received'],
+            'isActive' => true,
+            'createdOn' => '2026-01-02T03:04:05.1234567+00:00',
+        ]], JSON_THROW_ON_ERROR);
+
+        /** @var Hook[] $hooks */
+        $hooks = ObjectSerializer::deserialize($json, '\EConnect\Psb\Model\Hook[]');
+
+        self::assertCount(1, $hooks);
+        self::assertInstanceOf(Hook::class, $hooks[0]);
+        self::assertSame('hook-1', $hooks[0]->getId());
+        self::assertSame(['invoice-received'], $hooks[0]->getTopics());
+        self::assertTrue($hooks[0]->getIsActive());
+        self::assertSame('2026-01-02T03:04:05.123456+00:00', $hooks[0]->getCreatedOn()->format('Y-m-d\TH:i:s.uP'));
+        self::assertTrue($hooks[0]->valid());
+    }
+
+    public function testModelRoundTripsThroughJson(): void
+    {
+        $hook = new Hook([
+            'id' => 'hook-1',
+            'name' => 'Default',
+            'action' => 'https://example.test/hook',
+            'is_active' => false,
+            'created_on' => new \DateTime('2026-01-02T03:04:05+00:00'),
+        ]);
+
+        /** @var Hook $copy */
+        $copy = ObjectSerializer::deserialize(json_encode($hook, JSON_THROW_ON_ERROR), Hook::class);
+
+        self::assertSame($hook->getId(), $copy->getId());
+        self::assertSame($hook->getName(), $copy->getName());
+        self::assertSame($hook->getAction(), $copy->getAction());
+        self::assertFalse($copy->getIsActive());
+        self::assertEquals($hook->getCreatedOn(), $copy->getCreatedOn());
+    }
+}
diff --git a/test/Unit/OidcAuthenticatorTest.php b/test/Unit/OidcAuthenticatorTest.php
new file mode 100644
index 0000000..85661f4
--- /dev/null
+++ b/test/Unit/OidcAuthenticatorTest.php
@@ -0,0 +1,173 @@
+<?php
+
+declare(strict_types=1);
+
+namespace EConnect\Psb\Test\Unit;
+
+use EConnect\Psb\ApiException;
+use EConnect\Psb\Configuration;
+use EConnect\Psb\OidcAuthenticator;
+use GuzzleHttp\Psr7\HttpFactory;
+use GuzzleHttp\Psr7\Response;
+use Http\Client\Exception\NetworkException;
+use Http\Mock\Client;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Clock\MockClock;
+
+final class OidcAuthenticatorTest extends TestCase
+{
+    private Client $client;
+    private MockClock $clock;
+    private Configuration $config;
+    private OidcAuthenticator $authenticator;
+
+    protected function setUp(): void
+    {
+        $this->client = new Client();
+        $this->clock = new MockClock('2026-01-01 12:00:00');
+        $this->config = (new Configuration())
+            ->setHost('https://psb.example.test')
+            ->setUsername('jane')
+            ->setPassword('s3cr3t');
+
+        $factory = new HttpFactory();
+        $this->authenticator = new OidcAuthenticator($this->client, $factory, $factory, $this->clock, $this->config);
+    }
+
+    public function testAuthenticateFetchesTokenUsingDiscoveredEndpoint(): void
+    {
+        $this->queueSuccessfulLogin('token-1');
+
+        self::assertSame('token-1', $this->authenticator->authenticate('client-id', 'client-secret'));
+        self::assertSame('token-1', $this->config->getAccessToken());
+
+        [$discoveryRequest, $tokenRequest] = $this->client->getRequests();
+
+        self::assertSame('GET', $discoveryRequest->getMethod());
+        self::assertSame('https://identity.example.test/.well-known/openid-configuration', (string) $discoveryRequest->getUri());
+
+        self::assertSame('POST', $tokenRequest->getMethod());
+        self::assertSame('https://identity.example.test/connect/token', (string) $tokenRequest->getUri());
+        self::assertSame('application/x-www-form-urlencoded', $tokenRequest->getHeaderLine('Content-Type'));
+
+        parse_str((string) $tokenRequest->getBody(), $form);
+        self::assertSame([
+            'grant_type' => 'password',
+            'client_id' => 'client-id',
+            'client_secret' => 'client-secret',
+            'username' => 'jane',
+            'password' => 's3cr3t',
+            'scope' => 'ap',
+        ], $form);
+    }
+
+    public function testAuthenticateIgnoresTrailingSlashInHost(): void
+    {
+        $this->config->setHost('https://psb.example.test/');
+        $this->queueSuccessfulLogin('token-1');
+
+        $this->authenticator->authenticate('client-id', 'client-secret');
+
+        self::assertSame(
+            'https://identity.example.test/.well-known/openid-configuration',
+            (string) $this->client->getRequests()[0]->getUri()
+        );
+    }
+
+    public function testAuthenticateReusesTokenUntilShortlyBeforeExpiry(): void
+    {
+        $this->queueSuccessfulLogin('token-1', 3600);
+        $this->queueSuccessfulLogin('token-2', 3600);
+
+        $this->authenticator->authenticate('client-id', 'client-secret');
+
+        $this->clock->sleep(3600 - 61);
+        self::assertSame('token-1', $this->authenticator->authenticate('client-id', 'client-secret'));
+        self::assertCount(2, $this->client->getRequests());
+
+        // Within the leeway window the token is renewed instead of being sent while about to expire.
+        $this->clock->sleep(1);
+        self::assertSame('token-2', $this->authenticator->authenticate('client-id', 'client-secret'));
+        self::assertCount(4, $this->client->getRequests());
+    }
+
+    public function testAuthenticateReportsOAuthErrorDescription(): void
+    {
+        $this->client->addResponse($this->jsonResponse(200, ['token_endpoint' => 'https://identity.example.test/connect/token']));
+        $this->client->addResponse($this->jsonResponse(400, ['error' => 'invalid_grant', 'error_description' => 'invalid_username_or_password']));
+
+        try {
+            $this->authenticator->authenticate('client-id', 'client-secret');
+            self::fail('Expected an ApiException');
+        } catch (ApiException $e) {
+            self::assertSame('OIDC login failed: [400] invalid_username_or_password', $e->getMessage());
+            self::assertSame(400, $e->getCode());
+            self::assertStringContainsString('invalid_grant', (string) $e->getResponseBody());
+        }
+
+        self::assertSame('', $this->config->getAccessToken());
+    }
+
+    public function testAuthenticateWrapsNonJsonErrorResponse(): void
+    {
+        $this->client->addResponse(new Response(502, ['Content-Type' => 'text/html'], '<html>Bad Gateway</html>'));
+
+        $this->expectException(ApiException::class);
+        $this->expectExceptionMessage('OpenID discovery failed: [502] Bad Gateway');
+
+        $this->authenticator->authenticate('client-id', 'client-secret');
+    }
+
+    public function testAuthenticateFailsWhenTokenEndpointIsMissing(): void
+    {
+        $this->client->addResponse($this->jsonResponse(200, ['issuer' => 'https://identity.example.test']));
+
+        $this->expectException(ApiException::class);
+        $this->expectExceptionMessage('Missing token_endpoint in OpenID configuration.');
+
+        $this->authenticator->authenticate('client-id', 'client-secret');
+    }
+
+    public function testAuthenticateFailsWhenTokenResponseHasNoExpiry(): void
+    {
+        $this->client->addResponse($this->jsonResponse(200, ['token_endpoint' => 'https://identity.example.test/connect/token']));
+        $this->client->addResponse($this->jsonResponse(200, ['access_token' => 'token-1']));
+
+        $this->expectException(ApiException::class);
+        $this->expectExceptionMessage('OIDC login failed: missing access token or expiry.');
+
+        $this->authenticator->authenticate('client-id', 'client-secret');
+    }
+
+    public function testAuthenticateWrapsTransportErrors(): void
+    {
+        $factory = new HttpFactory();
+        $this->client->addException(new NetworkException('Connection refused', $factory->createRequest('GET', 'https://identity.example.test')));
+
+        try {
+            $this->authenticator->authenticate('client-id', 'client-secret');
+            self::fail('Expected an ApiException');
+        } catch (ApiException $e) {
+            self::assertSame('[0] Connection refused', $e->getMessage());
+            self::assertInstanceOf(NetworkException::class, $e->getPrevious());
+        }
+    }
+
+    private function queueSuccessfulLogin(string $token, int $expiresIn = 3600): void
+    {
+        $this->client->addResponse($this->jsonResponse(200, ['token_endpoint' => 'https://identity.example.test/connect/token']));
+        $this->client->addResponse($this->jsonResponse(200, [
+            'access_token' => $token,
+            'expires_in' => $expiresIn,
+            'token_type' => 'Bearer',
+        ]));
+    }
+
+    /**
+     * @param array<string, mixed> $body
+     */
+    private function jsonResponse(int $status, array $body): Response
+    {
+        return new Response($status, ['Content-Type' => 'application/json'], json_encode($body, JSON_THROW_ON_ERROR));
+    }
+}
diff --git a/test/Unit/SymfonyHttpClientTest.php b/test/Unit/SymfonyHttpClientTest.php
new file mode 100644
index 0000000..b409aad
--- /dev/null
+++ b/test/Unit/SymfonyHttpClientTest.php
@@ -0,0 +1,91 @@
+<?php
+
+declare(strict_types=1);
+
+namespace EConnect\Psb\Test\Unit;
+
+use EConnect\Psb\Api\MeApi;
+use EConnect\Psb\ApiException;
+use EConnect\Psb\Configuration;
+use EConnect\Psb\Model\User;
+use EConnect\Psb\OidcAuthenticator;
+use GuzzleHttp\Psr7\HttpFactory;
+use PHPUnit\Framework\TestCase;
+use Symfony\Component\Clock\NativeClock;
+use Symfony\Component\HttpClient\HttplugClient;
+use Symfony\Component\HttpClient\MockHttpClient;
+use Symfony\Component\HttpClient\Psr18Client;
+use Symfony\Component\HttpClient\Response\MockResponse;
+
+/**
+ * Runs the SDK on top of Symfony HttpClient, the PSR-18 / HTTPlug implementation used by Symfony applications.
+ */
+final class SymfonyHttpClientTest extends TestCase
+{
+    /** @var list<array{string, string, array<string, mixed>}> */
+    private array $requests = [];
+
+    public function testAuthenticatesAndCallsApiThroughSymfonyHttpClient(): void
+    {
+        $httpClient = $this->createHttpClient([
+            new MockResponse('{"token_endpoint":"https://identity.example.test/connect/token"}'),
+            new MockResponse('{"access_token":"access-token","expires_in":3600}'),
+            new MockResponse('{"name":"jane"}'),
+        ]);
+
+        $factory = new HttpFactory();
+        $psr18Client = new Psr18Client($httpClient, $factory, $factory);
+        $config = (new Configuration())
+            ->setHost('https://psb.example.test')
+            ->setUsername('jane')
+            ->setPassword('s3cr3t')
+            ->setApiKey('Subscription-Key', 'subscription-key');
+
+        (new OidcAuthenticator($psr18Client, $factory, $factory, new NativeClock(), $config))
+            ->authenticate('client-id', 'client-secret');
+
+        $user = (new MeApi($psr18Client, $config, new HttplugClient($httpClient, $factory, $factory), $factory, $factory, $factory))
+            ->getUser();
+
+        self::assertInstanceOf(User::class, $user);
+        self::assertSame('jane', $user->getName());
+
+        [, $url, $options] = $this->requests[2];
+        self::assertSame('https://psb.example.test/api/v1/me', $url);
+        self::assertContains('Authorization: Bearer access-token', $options['headers']);
+        self::assertContains('Subscription-Key: subscription-key', $options['headers']);
+    }
+
+    public function testAsyncRequestsResolveThroughHttplugClient(): void
+    {
+        $httpClient = $this->createHttpClient([
+            new MockResponse('{"name":"jane"}'),
+            new MockResponse('{"title":"Unauthorized"}', ['http_code' => 401]),
+        ]);
+
+        $factory = new HttpFactory();
+        $api = new MeApi(new Psr18Client($httpClient, $factory, $factory), new Configuration(), new HttplugClient($httpClient, $factory, $factory), $factory, $factory, $factory);
+
+        $user = $api->getUserAsync()->wait();
+
+        self::assertInstanceOf(User::class, $user);
+        self::assertSame('jane', $user->getName());
+
+        $this->expectException(ApiException::class);
+        $this->expectExceptionCode(401);
+
+        $api->getUserAsync()->wait();
+    }
+
+    /**
+     * @param list<MockResponse> $responses
+     */
+    private function createHttpClient(array $responses): MockHttpClient
+    {
+        return new MockHttpClient(function (string $method, string $url, array $options) use (&$responses): MockResponse {
+            $this->requests[] = [$method, $url, $options];
+
+            return array_shift($responses);
+        });
+    }
+}