diff --git a/CHANGELOG.md b/CHANGELOG.md
index 96c65266a2..bb035169c5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -65,6 +65,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   * `Elastica\Search::setOptionsAndQuery()`
   * `Elastica\Index::search()`
   * `Elastica\Index::createSearch()`
+* Removed classes [#2188](https://github.com/ruflin/Elastica/pull/2188)
+  * `Elastica\Connection`
+  * `Elastica\Connection\ConnectionPool`
+  * `Elastica\Connection\Strategy\CallbackStrategy`
+  * `Elastica\Connection\Strategy\RoundRobin`
+  * `Elastica\Connection\Strategy\Simple`
+  * `Elastica\Connection\Strategy\StrategyFactory`
+  * `Elastica\Connection\Strategy\StrategyInterface`
+* Removed `Elastica\Client::setLogger()` method [#2148](https://github.com/ruflin/Elastica/pull/2148)
 
 ### Added
 * Added support for PHP 8.2 [#2136](https://github.com/ruflin/Elastica/pull/2136)
@@ -79,6 +88,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 * Removed the JSONParseException class, which is replaced by \JsonException
 * Removed the JSONParseException test class
+* Removed `nyholm/dsn` as no longer needed.
+* Removed `symfony/deprecation-contracts` as no longer needed.
 ### Fixed
 * Fix types order in `Elastica\Query` to work with psalm & expand the `aggs` type to include raw arrays
 ### Security
diff --git a/composer.json b/composer.json
index d23331d6b8..dd19812664 100644
--- a/composer.json
+++ b/composer.json
@@ -17,12 +17,9 @@
     "require": {
         "php": "~8.0.0 || ~8.1.0 || ~8.2.0",
         "ext-json": "*",
-        "elastic/transport": "^8.4",
+        "elastic/transport": "^8.8",
         "elasticsearch/elasticsearch": "^8.4.1",
-        "guzzlehttp/psr7": "^2.0",
-        "nyholm/dsn": "^2.0.0",
-        "psr/log": "^1.0 || ^2.0 || ^3.0",
-        "symfony/deprecation-contracts": "^3.0"
+        "psr/log": "^1.0 || ^2.0 || ^3.0"
     },
     "require-dev": {
         "guzzlehttp/guzzle": "^7.2",
@@ -31,9 +28,11 @@
         "phpunit/phpunit": "^9.5",
         "symfony/phpunit-bridge": "^6.0"
     },
+    "conflict": {
+        "guzzlehttp/psr7": "<2.0.0"
+    },
     "suggest": {
         "aws/aws-sdk-php": "Allow using IAM authentication with Amazon ElasticSearch Service",
-        "guzzlehttp/guzzle": "Allow using guzzle as transport",
         "monolog/monolog": "Logging request"
     },
     "autoload": {
@@ -49,11 +48,12 @@
     "config": {
         "allow-plugins": {
             "php-http/discovery": true
-        }
+        },
+        "sort-packages": true
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "7.0.x-dev"
+            "dev-master": "8.0.x-dev"
         }
     }
 }
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 274eb46148..4f9f08ca91 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -60,11 +60,6 @@ parameters:
 			count: 1
 			path: tests/ClientFunctionalTest.php
 
-		-
-			message: "#^Parameter \\#1 \\$params of static method Elastica\\\\Connection\\:\\:create\\(\\) expects array\\|Elastica\\\\Connection, string given\\.$#"
-			count: 1
-			path: tests/ConnectionTest.php
-
 		-
 			message: "#^Access to an undefined property Elastica\\\\Document\\:\\:\\$field1\\.$#"
 			count: 1
diff --git a/src/Bulk.php b/src/Bulk.php
index 98aea084cf..cb31b6eeef 100644
--- a/src/Bulk.php
+++ b/src/Bulk.php
@@ -133,8 +133,12 @@ public function getActions(): array
      */
     public function addDocument(Document $document, ?string $opType = null): self
     {
-        if (!$document->hasRetryOnConflict() && $this->_client->hasConnection() && $this->_client->getConnection()->hasParam('retryOnConflict') && ($retry = $this->_client->getConnection()->getParam('retryOnConflict')) > 0) {
-            $document->setRetryOnConflict($retry);
+        if (!$document->hasRetryOnConflict()) {
+            $retry = $this->_client->getConfigValue('retryOnConflict', 0);
+
+            if ($retry > 0) {
+                $document->setRetryOnConflict($retry);
+            }
         }
 
         $action = AbstractDocumentAction::create($document, $opType);
@@ -161,8 +165,12 @@ public function addDocuments(array $documents, ?string $opType = null): self
      */
     public function addScript(AbstractScript $script, ?string $opType = null): self
     {
-        if (!$script->hasRetryOnConflict() && $this->_client->hasConnection() && $this->_client->getConnection()->hasParam('retryOnConflict') && ($retry = $this->_client->getConnection()->getParam('retryOnConflict')) > 0) {
-            $script->setRetryOnConflict($retry);
+        if (!$script->hasRetryOnConflict()) {
+            $retry = $this->_client->getConfigValue('retryOnConflict', 0);
+
+            if ($retry > 0) {
+                $script->setRetryOnConflict($retry);
+            }
         }
 
         $action = AbstractDocumentAction::create($script, $opType);
diff --git a/src/Client.php b/src/Client.php
index 521ddaa7af..780cd9567c 100644
--- a/src/Client.php
+++ b/src/Client.php
@@ -23,8 +23,6 @@
 use Elastica\Exception\ClientException;
 use Elastica\Exception\InvalidException;
 use Elastica\Script\AbstractScript;
-use GuzzleHttp\Psr7\Uri;
-use Http\Promise\Promise;
 use Psr\Http\Client\ClientInterface as HttpClientInterface;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
@@ -47,69 +45,25 @@ class Client implements ClientInterface
 
     private bool $elasticMetaHeader = true;
 
-    /**
-     * @var ClientConfiguration
-     */
-    protected $_config;
-
-    /**
-     * @var callable
-     */
-    protected $_callback;
+    protected ClientConfiguration $_config;
 
-    /**
-     * @var Connection\ConnectionPool
-     */
-    protected $_connectionPool;
-
-    /**
-     * @var RequestInterface|null
-     */
-    protected $_lastRequest;
+    protected ?RequestInterface $_lastRequest = null;
 
-    /**
-     * @var Elasticsearch|null
-     */
-    protected $_lastResponse;
+    protected ?Elasticsearch $_lastResponse = null;
 
-    /**
-     * @var LoggerInterface
-     */
-    protected $_logger;
+    protected LoggerInterface $_logger;
 
-    /**
-     * @var string
-     */
-    protected $_version;
+    protected ?string $_version = null;
 
-    /**
-     * The endpoint namespace storage.
-     */
-    protected array $namespace;
+    private Transport $_transport;
 
-    /**
-     * Creates a new Elastica client.
-     *
-     * @param array|string  $config   OPTIONAL Additional config or DSN of options
-     * @param callable|null $callback OPTIONAL Callback function which can be used to be notified about errors (for example connection down)
-     *
-     * @throws InvalidException
-     */
-    public function __construct($config = [], ?callable $callback = null, ?LoggerInterface $logger = null)
+    public function __construct(string|array $config = [], ?LoggerInterface $logger = null)
     {
-        if (\is_string($config)) {
-            $configuration = ClientConfiguration::fromDsn($config);
-        } elseif (\is_array($config)) {
-            $configuration = ClientConfiguration::fromArray($config);
-        } else {
-            throw new InvalidException('Config parameter must be an array or a string.');
-        }
+        $config = \is_string($config) ? ['hosts' => [$config]] : $config;
 
-        $this->_config = $configuration;
-        $this->_callback = $callback;
+        $this->_config = ClientConfiguration::fromArray($config);
         $this->_logger = $logger ?? new NullLogger();
-
-        $this->_initConnections();
+        $this->_transport = $this->_buildTransport($this->getConfig());
     }
 
     /**
@@ -125,7 +79,7 @@ public function getLogger(): LoggerInterface
      */
     public function getTransport(): Transport
     {
-        throw new \Exception('Not supported');
+        return $this->_transport;
     }
 
     /**
@@ -181,10 +135,9 @@ public function getResponseException(): bool
     /**
      * Get current version.
      *
-     * @throws MissingParameterException if a required parameter is missing
-     * @throws NoNodeAvailableException  if all the hosts are offline
-     * @throws ClientResponseException   if the status code of response is 4xx
-     * @throws ServerResponseException   if the status code of response is 5xx
+     * @throws NoNodeAvailableException if all the hosts are offline
+     * @throws ClientResponseException  if the status code of response is 4xx
+     * @throws ServerResponseException  if the status code of response is 5xx
      * @throws ClientException
      */
     public function getVersion(): string
@@ -262,36 +215,6 @@ public function getIndex(string $name): Index
         return new Index($this, $name);
     }
 
-    /**
-     * Adds a HTTP Header.
-     */
-    public function addHeader(string $header, string $value): self
-    {
-        if ($this->_config->has('headers')) {
-            $headers = $this->_config->get('headers');
-        } else {
-            $headers = [];
-        }
-        $headers[$header] = $value;
-        $this->_config->set('headers', $headers);
-
-        return $this;
-    }
-
-    /**
-     * Remove a HTTP Header.
-     */
-    public function removeHeader(string $header): self
-    {
-        if ($this->_config->has('headers')) {
-            $headers = $this->_config->get('headers');
-            unset($headers[$header]);
-            $this->_config->set('headers', $headers);
-        }
-
-        return $this;
-    }
-
     /**
      * Uses _bulk to send documents to the server.
      *
@@ -464,90 +387,20 @@ public function deleteDocuments(array $docs, array $requestParams = []): Respons
 
     /**
      * Returns the status object for all indices.
-     *
-     * @return Status
      */
-    public function getStatus()
+    public function getStatus(): Status
     {
         return new Status($this);
     }
 
     /**
      * Returns the current cluster.
-     *
-     * @return Cluster
      */
-    public function getCluster()
+    public function getCluster(): Cluster
     {
         return new Cluster($this);
     }
 
-    /**
-     * Establishes the client connections.
-     */
-    public function connect()
-    {
-        $this->_initConnections();
-    }
-
-    /**
-     * @return $this
-     */
-    public function addConnection(Connection $connection)
-    {
-        $this->_connectionPool->addConnection($connection);
-
-        return $this;
-    }
-
-    /**
-     * Determines whether a valid connection is available for use.
-     *
-     * @return bool
-     */
-    public function hasConnection()
-    {
-        return $this->_connectionPool->hasConnection();
-    }
-
-    /**
-     * @throws ClientException
-     *
-     * @return Connection
-     */
-    public function getConnection()
-    {
-        return $this->_connectionPool->getConnection();
-    }
-
-    /**
-     * @return Connection[]
-     */
-    public function getConnections()
-    {
-        return $this->_connectionPool->getConnections();
-    }
-
-    /**
-     * @return \Elastica\Connection\Strategy\StrategyInterface
-     */
-    public function getConnectionStrategy()
-    {
-        return $this->_connectionPool->getStrategy();
-    }
-
-    /**
-     * @param array|Connection[] $connections
-     *
-     * @return $this
-     */
-    public function setConnections(array $connections)
-    {
-        $this->_connectionPool->setConnections($connections);
-
-        return $this;
-    }
-
     /**
      * Deletes documents with the given ids, index, type from the index.
      *
@@ -627,46 +480,36 @@ public function bulk(array $params): ResponseSet
         return $bulk->send();
     }
 
-    public function baseBulk(array $params)
+    public function baseBulk(array $params): Response
     {
         return $this->toElasticaResponse($this->elasticClientBulk($params));
     }
 
-    public function sendRequest(RequestInterface $sentRequest): Elasticsearch|Promise
+    public function sendRequest(RequestInterface $request): Elasticsearch
     {
-        $connection = $this->getConnection();
-        $transport = $connection->getTransportObject();
-
-        $this->_lastRequest = $sentRequest;
+        $this->_lastRequest = $request;
         $this->_lastResponse = null;
 
         try {
-            $response = $transport->sendRequest($sentRequest);
+            $response = $this->_transport->sendRequest($request);
 
             $result = new Elasticsearch();
-            $result->setResponse($response, 'HEAD' === $sentRequest->getMethod() ? false : true);
+            $result->setResponse($response, 'HEAD' !== $request->getMethod());
 
             $this->_lastResponse = $result;
         } catch (ServerResponseException|NoNodeAvailableException $e) {
-            $this->_connectionPool->onFail($connection, $e, $this);
             $this->_logger->error('Elastica Request Failure', [
                 'exception' => $e,
-                'request' => $sentRequest,
-                'request_content' => \json_decode($sentRequest->getBody()->__toString(), true),
-                'retry' => $this->hasConnection(),
+                'request' => $request,
+                'request_content' => \json_decode($request->getBody()->__toString(), true),
             ]);
 
-            // In case there is no valid connection left, throw exception which caused the disabling of the connection.
-            if (!$this->hasConnection()) {
-                throw $e;
-            }
-
-            return $this->sendRequest($sentRequest);
+            throw $e;
         }
 
         $this->_logger->debug('Elastica Request', [
-            'request' => \json_decode($sentRequest->getBody()->__toString(), true),
-            'response' => 'HEAD' !== $sentRequest->getMethod() ? $result->asArray() : $result->asString(),
+            'request' => \json_decode($request->getBody()->__toString(), true),
+            'response' => 'HEAD' !== $request->getMethod() ? $result->asArray() : $result->asString(),
             'responseStatus' => $response->getStatusCode(),
         ]);
 
@@ -676,17 +519,14 @@ public function sendRequest(RequestInterface $sentRequest): Elasticsearch|Promis
     /**
      * Force merges all search indices.
      *
-     * @param array $args OPTIONAL Optional arguments
-     *
      * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/indices-forcemerge.html
      *
-     * @throws MissingParameterException if a required parameter is missing
-     * @throws NoNodeAvailableException  if all the hosts are offline
-     * @throws ClientResponseException   if the status code of response is 4xx
-     * @throws ServerResponseException   if the status code of response is 5xx
+     * @throws NoNodeAvailableException if all the hosts are offline
+     * @throws ClientResponseException  if the status code of response is 4xx
+     * @throws ServerResponseException  if the status code of response is 5xx
      * @throws ClientException
      */
-    public function forcemergeAll($args = []): Response
+    public function forcemergeAll(array $args = []): Response
     {
         return $this->toElasticaResponse($this->indices()->forcemerge($args));
     }
@@ -731,109 +571,20 @@ public function getLastResponse(): ?Elasticsearch
         return $this->_lastResponse;
     }
 
-    /**
-     * Replace the existing logger.
-     *
-     * @return $this
-     */
-    public function setLogger(LoggerInterface $logger)
-    {
-        $this->_logger = $logger;
-
-        return $this;
-    }
-
     public function toElasticaResponse(Elasticsearch|ResponseInterface $elasticsearchResponse): Response
     {
         return ResponseConverter::toElastica($elasticsearchResponse);
     }
 
-    /**
-     * Inits the client connections.
-     */
-    protected function _initConnections(): void
-    {
-        $connections = [];
-
-        foreach ($this->getConfig('connections') as $connection) {
-            $connections[] = Connection::create($this->_prepareConnectionParams($connection));
-        }
-
-        if ($this->_config->has('servers')) {
-            $servers = $this->_config->get('servers');
-            foreach ($servers as $server) {
-                $connections[] = Connection::create($this->_prepareConnectionParams($server));
-            }
-        }
-
-        // If no connections set, create default connection
-        if (!$connections) {
-            $connections[] = Connection::create($this->_prepareConnectionParams($this->getConfig()));
-        }
-
-        if (!$this->_config->has('connectionStrategy')) {
-            if (true === $this->getConfig('roundRobin')) {
-                $this->setConfigValue('connectionStrategy', 'RoundRobin');
-            } else {
-                $this->setConfigValue('connectionStrategy', 'Simple');
-            }
-        }
-
-        $strategy = Connection\Strategy\StrategyFactory::create($this->getConfig('connectionStrategy'));
-
-        $this->_connectionPool = new Connection\ConnectionPool($connections, $strategy, $this->_callback);
-    }
-
-    /**
-     * Creates a Connection params array from a Client or server config array.
-     */
-    protected function _prepareConnectionParams(array $config): array
-    {
-        $params = [];
-        $params['config'] = [];
-        foreach ($config as $key => $value) {
-            if (\in_array($key, ['bigintConversion', 'curl', 'headers', 'url'])) {
-                $params['config'][$key] = $value;
-            } else {
-                $params[$key] = $value;
-            }
-        }
-
-        $params['transport'] = $this->_buildTransport($config);
-
-        return $params;
-    }
-
     protected function _buildTransport(array $config): Transport
     {
+        $hosts = isset($config['hosts']) && \is_array($config['hosts']) ? $config['hosts'] : [ClientConfiguration::DEFAULT_HOST];
         $transportConfig = $config['transport_config'] ?? [];
-        $hosts = [];
-
-        if (isset($config['url'])) {
-            $hosts = [$config['url']];
-        } else {
-            if (isset($config['hosts'])) {
-                $hosts = $config['hosts'];
-            } else {
-                $hosts = [(string) Uri::fromParts([
-                    'scheme' => $config['schema'] ?? 'http',
-                    'host' => $config['host'] ?? Connection::DEFAULT_HOST,
-                    'port' => $config['port'] ?? Connection::DEFAULT_PORT,
-                    'path' => isset($config['path']) ? '/'.\ltrim($config['path'], '/') : '',
-                ]),
-                ];
-            }
-        }
 
-        // Transport builder
         $builder = TransportBuilder::create();
 
         $builder->setHosts($hosts);
-
-        // Logger
-        if (null !== $this->_logger) {
-            $builder->setLogger($this->_logger);
-        }
+        $builder->setLogger($this->_logger);
 
         // Http client
         if (isset($transportConfig['http_client'])) {
@@ -856,7 +607,7 @@ protected function _buildTransport(array $config): Transport
 
         // Node Pool
         if (isset($transportConfig['node_pool'])) {
-            $builder->setNodePool($config['node_pool']);
+            $builder->setNodePool($transportConfig['node_pool']);
         }
 
         $transport = $builder->build();
@@ -874,10 +625,11 @@ protected function _buildTransport(array $config): Transport
         }
 
         // API key
-        if (isset($config['api_key']) && !empty($config['api_key'])) {
-            if (isset($config['username']) && !empty($config['username'])) {
-                throw new InvalidException('You cannot use APIKey and Basic Authenication together');
+        if (!empty($config['api_key'])) {
+            if (!empty($config['username'])) {
+                throw new InvalidException('You cannot use APIKey and Basic Authentication together.');
             }
+
             $transport->setHeader('Authorization', \sprintf('ApiKey %s', $config['api_key']));
         }
 
@@ -897,18 +649,15 @@ protected function _buildTransport(array $config): Transport
      */
     protected function isSymfonyHttpClient(Transport $transport): bool
     {
-        if (false !== \strpos(\get_class($transport->getClient()), 'Symfony\Component\HttpClient')) {
+        if (\str_contains($transport->getClient()::class, 'Symfony\Component\HttpClient')) {
             return true;
         }
+
         try {
-            if (false !== \strpos(\get_class($transport->getAsyncClient()), 'Symfony\Component\HttpClient')) {
-                return true;
-            }
+            return \str_contains($transport->getAsyncClient()::class, 'Symfony\Component\HttpClient');
         } catch (NoAsyncClientException $e) {
             return false;
         }
-
-        return false;
     }
 
     protected function setTransportClientOptions(HttpClientInterface $client, array $config, array $clientOptions = []): HttpClientInterface
@@ -916,16 +665,13 @@ protected function setTransportClientOptions(HttpClientInterface $client, array
         if (empty($config) && empty($clientOptions)) {
             return $client;
         }
-        $class = \get_class($client);
-        if (!isset(AdapterOptions::HTTP_ADAPTERS[$class])) {
-            throw new HttpClientException(\sprintf('The HTTP client %s is not supported for custom options', $class));
-        }
-        $adapterClass = AdapterOptions::HTTP_ADAPTERS[$class];
-        if (!\class_exists($adapterClass) || !\in_array(AdapterInterface::class, \class_implements($adapterClass))) {
+
+        $adapterClass = AdapterOptions::HTTP_ADAPTERS[$client::class] ?? throw new HttpClientException(\sprintf('The HTTP client %s is not supported for custom options', $client::class));
+
+        if (!\class_exists($adapterClass) || !\in_array(AdapterInterface::class, \class_implements($adapterClass), true)) {
             throw new HttpClientException(\sprintf('The class %s does not exists or does not implement %s', $adapterClass, AdapterInterface::class));
         }
-        $adapter = new $adapterClass();
 
-        return $adapter->setConfig($client, $config, $clientOptions);
+        return (new $adapterClass())->setConfig($client, $config, $clientOptions);
     }
 }
diff --git a/src/ClientConfiguration.php b/src/ClientConfiguration.php
index 61020e5d05..f518e5d18f 100644
--- a/src/ClientConfiguration.php
+++ b/src/ClientConfiguration.php
@@ -3,10 +3,6 @@
 namespace Elastica;
 
 use Elastica\Exception\InvalidException;
-use Nyholm\Dsn\Configuration\Url;
-use Nyholm\Dsn\DsnParser;
-use Nyholm\Dsn\Exception\ExceptionInterface as DsnException;
-use Nyholm\Dsn\Exception\FunctionNotSupportedException;
 
 /**
  * Elastica client configuration.
@@ -15,6 +11,8 @@
  */
 class ClientConfiguration
 {
+    public const DEFAULT_HOST = 'localhost:9200';
+
     /**
      * Config with defaults.
      *
@@ -22,25 +20,15 @@ class ClientConfiguration
      * bigintConversion: Set to true to enable the JSON bigint to string conversion option (see issue #717)
      *
      * @var array{
-     *        host: string|null,
-     *        port: string|null,
-     *        path: string|null,
-     *        url:string|null,
-     *        connections: array<array-key, mixed>,
-     *        roundRobin: bool,
-     *        retryOnConflict: int,
-     *        username: string|null,
-     *        password: string|null,
-     *        transport_config: array<array-key, mixed>,
+     *     hosts: list<string>,
+     *     retryOnConflict: int,
+     *     username: string|null,
+     *     password: string|null,
+     *     transport_config: array<array-key, mixed>,
      * }
      */
-    protected $configuration = [
-        'host' => null,
-        'port' => null,
-        'path' => null,
-        'url' => null,
-        'connections' => [], // host, port, path, transport_config -> [http_client, http_client_config, http_client_options, node_pool], username, password
-        'roundRobin' => false,
+    protected array $configuration = [
+        'hosts' => [self::DEFAULT_HOST],
         'retryOnConflict' => 0,
         'username' => null,
         'password' => null,
@@ -62,51 +50,6 @@ public static function fromArray(array $config): self
         return $clientConfiguration;
     }
 
-    /**
-     * Create configuration from Dsn string. Example of valid DSN strings:
-     * - http://localhost
-     * - http://foo:bar@localhost:1234?timeout=4&persistant=false
-     * - pool(http://127.0.0.1 http://127.0.0.2/bar?timeout=4).
-     */
-    public static function fromDsn(string $dsnString): self
-    {
-        try {
-            $func = DsnParser::parseFunc($dsnString);
-        } catch (DsnException $e) {
-            throw new InvalidException(\sprintf('DSN "%s" is invalid.', $dsnString), 0, $e);
-        }
-
-        if ('dsn' === $func->getName()) {
-            /** @var Url $dsn */
-            $dsn = $func->first();
-            $clientConfiguration = self::fromArray(self::parseDsn($dsn));
-        } elseif ('pool' === $func->getName()) {
-            $connections = [];
-            $clientConfiguration = new static();
-            /** @var Url $arg */
-            foreach ($func->getArguments() as $arg) {
-                $connections[] = self::parseDsn($arg);
-            }
-            $clientConfiguration->set('connections', $connections);
-        } else {
-            throw new FunctionNotSupportedException($dsnString, $func->getName());
-        }
-
-        foreach ($func->getParameters() as $optionName => $optionValue) {
-            if ('false' === $optionValue) {
-                $optionValue = false;
-            } elseif ('true' === $optionValue) {
-                $optionValue = true;
-            } elseif (\is_numeric($optionValue)) {
-                $optionValue = (int) $optionValue;
-            }
-
-            $clientConfiguration->set($optionName, $optionValue);
-        }
-
-        return $clientConfiguration;
-    }
-
     /**
      * Returns a specific config key or the whole config array if not set.
      *
@@ -170,39 +113,4 @@ public function add(string $key, $value): void
             }
         }
     }
-
-    private static function parseDsn(Url $dsn): array
-    {
-        $data = ['host' => $dsn->getHost()];
-
-        if (null !== $dsn->getUser()) {
-            $data['username'] = $dsn->getUser();
-        }
-
-        if (null !== $dsn->getPassword()) {
-            $data['password'] = $dsn->getPassword();
-        }
-
-        if (null !== $dsn->getPort()) {
-            $data['port'] = $dsn->getPort();
-        }
-
-        if (null !== $dsn->getPath()) {
-            $data['path'] = $dsn->getPath();
-        }
-
-        foreach ($dsn->getParameters() as $optionName => $optionValue) {
-            if ('false' === $optionValue) {
-                $optionValue = false;
-            } elseif ('true' === $optionValue) {
-                $optionValue = true;
-            } elseif (\is_numeric($optionValue)) {
-                $optionValue = (int) $optionValue;
-            }
-
-            $data[$optionName] = $optionValue;
-        }
-
-        return $data;
-    }
 }
diff --git a/src/Connection.php b/src/Connection.php
deleted file mode 100644
index 8779e27e40..0000000000
--- a/src/Connection.php
+++ /dev/null
@@ -1,262 +0,0 @@
-<?php
-
-namespace Elastica;
-
-use Elastic\Transport\Transport;
-use Elastica\Exception\InvalidException;
-
-/**
- * Elastica connection instance to an elasticasearch node.
- *
- * @author   Nicolas Ruflin <spam@ruflin.com>
- */
-class Connection extends Param
-{
-    /**
-     * Default elastic search port.
-     */
-    public const DEFAULT_PORT = 9200;
-
-    /**
-     * Default host.
-     */
-    public const DEFAULT_HOST = 'localhost';
-
-    /**
-     * Default transport.
-     *
-     * @var string
-     */
-    public const DEFAULT_TRANSPORT = 'Http';
-
-    /**
-     * Default compression.
-     *
-     * @var bool
-     */
-    public const DEFAULT_COMPRESSION = false;
-
-    /**
-     * Creates a new connection object. A connection is enabled by default.
-     *
-     * @param array $params OPTIONAL Connection params: host, port. All are optional
-     */
-    public function __construct(array $params = [])
-    {
-        $this->setParams($params);
-        $this->setEnabled(true);
-
-        // Set empty config param if not exists
-        if (!$this->hasParam('config')) {
-            $this->setParam('config', []);
-        }
-    }
-
-    /**
-     * @return int Server port
-     */
-    public function getPort()
-    {
-        return $this->hasParam('port') ? $this->getParam('port') : self::DEFAULT_PORT;
-    }
-
-    /**
-     * @param int $port
-     *
-     * @return $this
-     */
-    public function setPort($port)
-    {
-        return $this->setParam('port', (int) $port);
-    }
-
-    /**
-     * @return string Host
-     */
-    public function getHost()
-    {
-        return $this->hasParam('host') ? $this->getParam('host') : self::DEFAULT_HOST;
-    }
-
-    /**
-     * @param string $host
-     *
-     * @return $this
-     */
-    public function setHost($host)
-    {
-        return $this->setParam('host', $host);
-    }
-
-    public function getTransport(): Transport
-    {
-        return $this->getParam('transport');
-    }
-
-    /**
-     * @return $this
-     */
-    public function setTransport(Transport $transport)
-    {
-        return $this->setParam('transport', $transport);
-    }
-
-    /**
-     * @return bool
-     */
-    public function hasCompression()
-    {
-        return (bool) $this->hasParam('compression') ? $this->getParam('compression') : self::DEFAULT_COMPRESSION;
-    }
-
-    /**
-     * @param bool $compression
-     *
-     * @return $this
-     */
-    public function setCompression($compression = null)
-    {
-        return $this->setParam('compression', $compression);
-    }
-
-    /**
-     * @return string
-     */
-    public function getPath()
-    {
-        return $this->hasParam('path') ? $this->getParam('path') : '';
-    }
-
-    /**
-     * @param string $path
-     *
-     * @return $this
-     */
-    public function setPath($path)
-    {
-        return $this->setParam('path', $path);
-    }
-
-    /**
-     * Enables a connection.
-     *
-     * @param bool $enabled OPTIONAL (default = true)
-     *
-     * @return $this
-     */
-    public function setEnabled($enabled = true)
-    {
-        return $this->setParam('enabled', $enabled);
-    }
-
-    /**
-     * @return bool True if enabled
-     */
-    public function isEnabled()
-    {
-        return (bool) $this->getParam('enabled');
-    }
-
-    /**
-     * Returns an instance of the transport type.
-     *
-     * @return Transport Transport object
-     */
-    public function getTransportObject(): Transport
-    {
-        return $this->getTransport();
-    }
-
-    /**
-     * @return $this
-     */
-    public function setConfig(array $config)
-    {
-        return $this->setParam('config', $config);
-    }
-
-    /**
-     * @param string $key
-     * @param mixed  $value
-     *
-     * @return $this
-     */
-    public function addConfig($key, $value)
-    {
-        $this->_params['config'][$key] = $value;
-
-        return $this;
-    }
-
-    /**
-     * @param string $key
-     *
-     * @return bool
-     */
-    public function hasConfig($key)
-    {
-        $config = $this->getConfig();
-
-        return isset($config[$key]);
-    }
-
-    /**
-     * Returns a specific config key or the whole
-     * config array if not set.
-     *
-     * @param string $key Config key
-     *
-     * @throws InvalidException
-     *
-     * @return array|bool|int|string|null Config value
-     */
-    public function getConfig($key = '')
-    {
-        $config = $this->getParam('config');
-        if (empty($key)) {
-            return $config;
-        }
-
-        if (!\array_key_exists($key, $config)) {
-            throw new InvalidException('Config key is not set: '.$key);
-        }
-
-        return $config[$key];
-    }
-
-    /**
-     * @param array|Connection $params Params to create a connection
-     *
-     * @throws Exception\InvalidException
-     *
-     * @return self
-     */
-    public static function create($params = [])
-    {
-        if (\is_array($params)) {
-            return new static($params);
-        }
-
-        if ($params instanceof self) {
-            return $params;
-        }
-
-        throw new InvalidException('Invalid data type');
-    }
-
-    /**
-     * @return string|null User
-     */
-    public function getUsername()
-    {
-        return $this->hasParam('username') ? $this->getParam('username') : null;
-    }
-
-    /**
-     * @return string|null Password
-     */
-    public function getPassword()
-    {
-        return $this->hasParam('password') ? $this->getParam('password') : null;
-    }
-}
diff --git a/src/Connection/ConnectionPool.php b/src/Connection/ConnectionPool.php
deleted file mode 100644
index 116fda3490..0000000000
--- a/src/Connection/ConnectionPool.php
+++ /dev/null
@@ -1,101 +0,0 @@
-<?php
-
-namespace Elastica\Connection;
-
-use Elastica\Client;
-use Elastica\Connection;
-use Elastica\Connection\Strategy\StrategyInterface;
-use Elastica\Exception\ClientException;
-
-/**
- * Description of ConnectionPool.
- *
- * @author chabior
- */
-class ConnectionPool
-{
-    /**
-     * @var array|Connection[] Connections array
-     */
-    protected $_connections;
-
-    /**
-     * @var StrategyInterface Strategy for connection
-     */
-    protected $_strategy;
-
-    /**
-     * @var callable|null Function called on connection fail
-     */
-    protected $_callback;
-
-    public function __construct(array $connections, StrategyInterface $strategy, ?callable $callback = null)
-    {
-        $this->_connections = $connections;
-        $this->_strategy = $strategy;
-        $this->_callback = $callback;
-    }
-
-    /**
-     * @return $this
-     */
-    public function addConnection(Connection $connection): self
-    {
-        $this->_connections[] = $connection;
-
-        return $this;
-    }
-
-    /**
-     * @param Connection[] $connections
-     *
-     * @return $this
-     */
-    public function setConnections(array $connections): self
-    {
-        $this->_connections = $connections;
-
-        return $this;
-    }
-
-    public function hasConnection(): bool
-    {
-        foreach ($this->_connections as $connection) {
-            if ($connection->isEnabled()) {
-                return true;
-            }
-        }
-
-        return false;
-    }
-
-    /**
-     * @return Connection[]
-     */
-    public function getConnections(): array
-    {
-        return $this->_connections;
-    }
-
-    /**
-     * @throws ClientException
-     */
-    public function getConnection(): Connection
-    {
-        return $this->_strategy->getConnection($this->getConnections());
-    }
-
-    public function onFail(Connection $connection, \Exception $e, Client $client): void
-    {
-        $connection->setEnabled(false);
-
-        if ($this->_callback) {
-            ($this->_callback)($connection, $e, $client);
-        }
-    }
-
-    public function getStrategy(): StrategyInterface
-    {
-        return $this->_strategy;
-    }
-}
diff --git a/src/Connection/Strategy/CallbackStrategy.php b/src/Connection/Strategy/CallbackStrategy.php
deleted file mode 100644
index 1507f01ddc..0000000000
--- a/src/Connection/Strategy/CallbackStrategy.php
+++ /dev/null
@@ -1,31 +0,0 @@
-<?php
-
-namespace Elastica\Connection\Strategy;
-
-use Elastica\Connection;
-
-/**
- * Description of CallbackStrategy.
- *
- * @author chabior
- */
-class CallbackStrategy implements StrategyInterface
-{
-    /**
-     * @var callable
-     */
-    protected $_callback;
-
-    public function __construct(callable $callback)
-    {
-        $this->_callback = $callback;
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getConnection(array $connections): Connection
-    {
-        return ($this->_callback)($connections);
-    }
-}
diff --git a/src/Connection/Strategy/RoundRobin.php b/src/Connection/Strategy/RoundRobin.php
deleted file mode 100644
index 661ee2924e..0000000000
--- a/src/Connection/Strategy/RoundRobin.php
+++ /dev/null
@@ -1,23 +0,0 @@
-<?php
-
-namespace Elastica\Connection\Strategy;
-
-use Elastica\Connection;
-
-/**
- * Description of RoundRobin.
- *
- * @author chabior
- */
-class RoundRobin extends Simple
-{
-    /**
-     * {@inheritdoc}
-     */
-    public function getConnection(array $connections): Connection
-    {
-        \shuffle($connections);
-
-        return parent::getConnection($connections);
-    }
-}
diff --git a/src/Connection/Strategy/Simple.php b/src/Connection/Strategy/Simple.php
deleted file mode 100644
index 822bd50638..0000000000
--- a/src/Connection/Strategy/Simple.php
+++ /dev/null
@@ -1,28 +0,0 @@
-<?php
-
-namespace Elastica\Connection\Strategy;
-
-use Elastica\Connection;
-use Elastica\Exception\ClientException;
-
-/**
- * Description of SimpleStrategy.
- *
- * @author chabior
- */
-class Simple implements StrategyInterface
-{
-    /**
-     * {@inheritdoc}
-     */
-    public function getConnection(array $connections): Connection
-    {
-        foreach ($connections as $connection) {
-            if ($connection->isEnabled()) {
-                return $connection;
-            }
-        }
-
-        throw new ClientException('No enabled connection');
-    }
-}
diff --git a/src/Connection/Strategy/StrategyFactory.php b/src/Connection/Strategy/StrategyFactory.php
deleted file mode 100644
index 1c0dc1fef2..0000000000
--- a/src/Connection/Strategy/StrategyFactory.php
+++ /dev/null
@@ -1,43 +0,0 @@
-<?php
-
-namespace Elastica\Connection\Strategy;
-
-use Elastica\Exception\InvalidException;
-
-/**
- * Description of StrategyFactory.
- *
- * @author chabior
- */
-class StrategyFactory
-{
-    /**
-     * @param callable|mixed|StrategyInterface|string $strategyName
-     *
-     * @throws InvalidException
-     */
-    public static function create($strategyName): StrategyInterface
-    {
-        if ($strategyName instanceof StrategyInterface) {
-            return $strategyName;
-        }
-
-        if (\is_callable($strategyName)) {
-            return new CallbackStrategy($strategyName);
-        }
-
-        if (\is_string($strategyName)) {
-            $predefinedStrategy = '\\Elastica\\Connection\\Strategy\\'.$strategyName;
-
-            if (\class_exists($predefinedStrategy) && \is_subclass_of($predefinedStrategy, StrategyInterface::class)) {
-                return new $predefinedStrategy();
-            }
-
-            if (\class_exists($strategyName) && \is_subclass_of($strategyName, StrategyInterface::class)) {
-                return new $strategyName();
-            }
-        }
-
-        throw new InvalidException('Can\'t create strategy instance by given argument');
-    }
-}
diff --git a/src/Connection/Strategy/StrategyInterface.php b/src/Connection/Strategy/StrategyInterface.php
deleted file mode 100644
index 3d28ea1a69..0000000000
--- a/src/Connection/Strategy/StrategyInterface.php
+++ /dev/null
@@ -1,18 +0,0 @@
-<?php
-
-namespace Elastica\Connection\Strategy;
-
-use Elastica\Connection;
-
-/**
- * Description of AbstractStrategy.
- *
- * @author chabior
- */
-interface StrategyInterface
-{
-    /**
-     * @param Connection[] $connections
-     */
-    public function getConnection(array $connections): Connection;
-}
diff --git a/tests/Base.php b/tests/Base.php
index e9337ce157..6adf4d6209 100644
--- a/tests/Base.php
+++ b/tests/Base.php
@@ -2,9 +2,11 @@
 
 namespace Elastica\Test;
 
+use Elastic\Transport\NodePool\Resurrect\NoResurrect;
+use Elastic\Transport\NodePool\Selector\RoundRobin;
 use Elastica\Client;
-use Elastica\Connection;
 use Elastica\Index;
+use Elastica\Test\Transport\NodePool\TraceableSimpleNodePool;
 use PHPUnit\Framework\TestCase;
 use PHPUnit\Util\Test as TestUtil;
 use Psr\Log\LoggerInterface;
@@ -46,38 +48,38 @@ protected static function showDeprecated(): void
     /**
      * @param array $params Additional configuration params. Host and Port are already set
      */
-    protected function _getClient(array $params = [], ?callable $callback = null, ?LoggerInterface $logger = null): Client
+    protected function _getClient(array $params = [], ?LoggerInterface $logger = null): Client
     {
-        $config = [
-            'host' => $this->_getHost(),
-            'port' => $this->_getPort(),
-        ];
+        $config = $params ?: [$this->_getHost().':'.$this->_getPort()];
 
-        $config = \array_merge($config, $params);
+        $config['transport_config']['node_pool'] = $config['transport_config']['node_pool'] ?? new TraceableSimpleNodePool(
+            new RoundRobin(),
+            new NoResurrect()
+        );
 
-        return new Client($config, $callback, $logger);
+        return new Client($config, $logger);
     }
 
     protected function _getHost(): string
     {
-        return \getenv('ES_HOST') ?: Connection::DEFAULT_HOST;
+        return \getenv('ES_HOST') ?: 'localhost';
     }
 
     protected function _getPort(): int
     {
-        return \getenv('ES_PORT') ?: Connection::DEFAULT_PORT;
+        return \getenv('ES_PORT') ?: 9200;
     }
 
     protected function _getProxyUrl(): string
     {
-        $proxyHost = \getenv('PROXY_HOST') ?: Connection::DEFAULT_HOST;
+        $proxyHost = \getenv('PROXY_HOST') ?: 'localhost';
 
         return 'http://'.$proxyHost.':8000';
     }
 
     protected function _getProxyUrl403(): string
     {
-        $proxyHost = \getenv('PROXY_HOST') ?: Connection::DEFAULT_HOST;
+        $proxyHost = \getenv('PROXY_HOST') ?: 'localhost';
 
         return 'http://'.$proxyHost.':8001';
     }
diff --git a/tests/BulkTest.php b/tests/BulkTest.php
index 4e9c06cd47..c8fd59c333 100644
--- a/tests/BulkTest.php
+++ b/tests/BulkTest.php
@@ -705,7 +705,7 @@ public function testRetry(): void
         $this->assertEquals(5, $metadata['retry_on_conflict']);
 
         // Test retry via client
-        $client->getConnection()->setParam('retryOnConflict', 5);
+        $client->setConfigValue('retryOnConflict', 5);
         $doc2 = new Document('2', ['name' => 'Invisible Woman']);
         $doc2->setOpType(Action::OP_TYPE_UPDATE);
 
diff --git a/tests/ClientConfigurationTest.php b/tests/ClientConfigurationTest.php
index 4bc6c274a3..5566843811 100644
--- a/tests/ClientConfigurationTest.php
+++ b/tests/ClientConfigurationTest.php
@@ -13,96 +13,12 @@
  */
 class ClientConfigurationTest extends TestCase
 {
-    public function testInvalidDsn(): void
-    {
-        $this->expectException(InvalidException::class);
-        $this->expectExceptionMessage('DSN "test foo" is invalid.');
-
-        ClientConfiguration::fromDsn('test foo');
-    }
-
-    public function testInvalidDsnPortOnly(): void
-    {
-        $this->expectException(InvalidException::class);
-        $this->expectExceptionMessage('DSN ":0" is invalid.');
-
-        ClientConfiguration::fromDsn(':0');
-    }
-
-    public function testFromSimpleDsn(): void
-    {
-        $configuration = ClientConfiguration::fromDsn('192.168.1.1:9201');
-
-        $expected = [
-            'host' => '192.168.1.1',
-            'port' => 9201,
-            'path' => null,
-            'url' => null,
-            'connections' => [],
-            'roundRobin' => false,
-            'retryOnConflict' => 0,
-            'username' => null,
-            'password' => null,
-            'transport_config' => [],
-        ];
-
-        $this->assertEquals($expected, $configuration->getAll());
-    }
-
-    public function testFromDsnWithParameters(): void
-    {
-        $configuration = ClientConfiguration::fromDsn('https://user:p4ss@foo.com:9201/my-path?roundRobin=true&retryOnConflict=2&extra=abc');
-        $expected = [
-            'host' => 'foo.com',
-            'port' => 9201,
-            'path' => '/my-path',
-            'url' => null,
-            'connections' => [],
-            'roundRobin' => true,
-            'retryOnConflict' => 2,
-            'username' => 'user',
-            'password' => 'p4ss',
-            'extra' => 'abc',
-            'transport_config' => [],
-        ];
-
-        $this->assertEquals($expected, $configuration->getAll());
-    }
-
-    public function testFromDsnWithPool(): void
-    {
-        $configuration = ClientConfiguration::fromDsn('pool(http://nicolas@127.0.0.1 http://127.0.0.2/bar?timeout=4)?extra=abc&username=tobias');
-        $expected = [
-            'host' => null,
-            'port' => null,
-            'path' => null,
-            'url' => null,
-            'connections' => [
-                ['host' => '127.0.0.1', 'username' => 'nicolas'],
-                ['host' => '127.0.0.2', 'path' => '/bar', 'timeout' => 4],
-            ],
-            'roundRobin' => false,
-            'retryOnConflict' => 0,
-            'username' => 'tobias',
-            'password' => null,
-            'extra' => 'abc',
-            'transport_config' => [],
-        ];
-
-        $this->assertEquals($expected, $configuration->getAll());
-    }
-
     public function testFromEmptyArray(): void
     {
         $configuration = ClientConfiguration::fromArray([]);
 
         $expected = [
-            'host' => null,
-            'port' => null,
-            'path' => null,
-            'url' => null,
-            'connections' => [], // host, port, path, timeout, transport, compression, timeout, username, password, config -> (curl, headers, url)
-            'roundRobin' => false,
+            'hosts' => [ClientConfiguration::DEFAULT_HOST],
             'retryOnConflict' => 0,
             'username' => null,
             'password' => null,
@@ -120,12 +36,7 @@ public function testFromArray(): void
         ]);
 
         $expected = [
-            'host' => null,
-            'port' => null,
-            'path' => null,
-            'url' => null,
-            'connections' => [], // host, port, path, timeout, transport, compression, timeout, username, password, config -> (curl, headers, url)
-            'roundRobin' => false,
+            'hosts' => [ClientConfiguration::DEFAULT_HOST],
             'retryOnConflict' => 0,
             'username' => 'Jdoe',
             'password' => null,
@@ -139,7 +50,7 @@ public function testFromArray(): void
     public function testHas(): void
     {
         $configuration = new ClientConfiguration();
-        $this->assertTrue($configuration->has('host'));
+        $this->assertTrue($configuration->has('hosts'));
         $this->assertFalse($configuration->has('inexistantKey'));
     }
 
@@ -148,12 +59,7 @@ public function testGet(): void
         $configuration = new ClientConfiguration();
 
         $expected = [
-            'host' => null,
-            'port' => null,
-            'path' => null,
-            'url' => null,
-            'connections' => [],
-            'roundRobin' => false,
+            'hosts' => [ClientConfiguration::DEFAULT_HOST],
             'retryOnConflict' => 0,
             'username' => null,
             'password' => null,
diff --git a/tests/ClientFunctionalTest.php b/tests/ClientFunctionalTest.php
index ddc2c82677..78bf18b752 100644
--- a/tests/ClientFunctionalTest.php
+++ b/tests/ClientFunctionalTest.php
@@ -5,15 +5,13 @@
 use Elastic\Elasticsearch\Response\Elasticsearch;
 use Elastic\Elasticsearch\Transport\Adapter\AdapterOptions;
 use Elastic\Transport\Exception\NoNodeAvailableException;
-use Elastic\Transport\TransportBuilder;
 use Elastica\Bulk;
 use Elastica\Bulk\ResponseSet;
-use Elastica\Client;
-use Elastica\Connection;
 use Elastica\Document;
 use Elastica\Exception\NotFoundException;
 use Elastica\Script\Script;
 use Elastica\Test\Base as BaseTest;
+use Elastica\Test\Transport\NodePool\TraceableSimpleNodePool;
 use GuzzleHttp\RequestOptions;
 use Psr\Http\Client\ClientInterface as HttpClientInterface;
 use Psr\Http\Message\RequestInterface;
@@ -29,7 +27,7 @@ public function testConnectionErrors(): void
     {
         $this->expectException(NoNodeAvailableException::class);
 
-        $client = $this->_getClient(['host' => 'foo.bar', 'port' => '9201']);
+        $client = $this->_getClient(['hosts' => ['foo.bar:9201']]);
         $client->getVersion();
     }
 
@@ -37,15 +35,7 @@ public function testClientBadHost(): void
     {
         $this->expectException(NoNodeAvailableException::class);
 
-        $client = $this->_getClient(['host' => 'localhost', 'port' => '9201']);
-        $client->getVersion();
-    }
-
-    public function testClientBadHostWithTimeout(): void
-    {
-        $this->expectException(NoNodeAvailableException::class);
-
-        $client = $this->_getClient(['host' => 'foo.bar', 'timeout' => 10]);
+        $client = $this->_getClient(['hosts' => ['localhost:9201']]);
         $client->getVersion();
     }
 
@@ -58,7 +48,7 @@ public function testGetVersion(): void
     public function testConnectionsArray(): void
     {
         // Creates a new index 'xodoa' and a type 'user' inside this index
-        $client = $this->_getClient(['connections' => [['host' => $this->_getHost(), 'port' => 9200]]]);
+        $client = $this->_getClient(['hosts' => [$this->_getHost().':9200']]);
         $index = $client->getIndex('elastica_test1');
         $index->create([], [
             'recreate' => true,
@@ -92,10 +82,12 @@ public function testConnectionsArray(): void
     public function testTwoServersSame(): void
     {
         // Creates a new index 'xodoa' and a type 'user' inside this index
-        $client = $this->_getClient(['connections' => [
-            ['host' => $this->_getHost(), 'port' => 9200],
-            ['host' => $this->_getHost(), 'port' => 9200],
-        ]]);
+        $client = $this->_getClient([
+            'hosts' => [
+                $this->_getHost().':9200',
+                $this->_getHost().':9200',
+            ],
+        ]);
         $index = $client->getIndex('elastica_test1');
         $index->create([], [
             'recreate' => true,
@@ -359,148 +351,63 @@ public function testDeleteIdsIdxObjectTypeObject(): void
 
     public function testOneInvalidConnection(): void
     {
-        $client = $this->_getClient();
-
-        $httpClientOptions = [
-            RequestOptions::TIMEOUT => 1,
-            RequestOptions::CONNECT_TIMEOUT => 1,
-        ];
-
-        $transportConnectionBuilder1 = TransportBuilder::create();
-        $transportConnectionBuilder1->setHosts([$this->_getHost().':9100']);
-        $transportConnectionBuilder1->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder2 = TransportBuilder::create();
-        $transportConnectionBuilder2->setHosts([$this->_getHost().':9200']);
-        $transportConnectionBuilder2->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        // First connection work, second should not work
-        $connection1 = new Connection(['port' => '9100', 'timeout' => 2, 'host' => $this->_getHost(), 'transport' => $transportConnectionBuilder1->build()]);
-        $connection2 = new Connection(['port' => '9200', 'timeout' => 2, 'host' => $this->_getHost(), 'transport' => $transportConnectionBuilder2->build()]);
-
-        $client->setConnections([$connection1, $connection2]);
+        $client = $this->_getClient([
+            'hosts' => [
+                // First connection is invalid and second should work
+                $this->_getHost().':9999',
+                $this->_getHost().':9200',
+            ],
+            'transport_config' => [
+                'http_client_options' => [
+                    RequestOptions::TIMEOUT => 1,
+                    RequestOptions::CONNECT_TIMEOUT => 1,
+                ],
+            ],
+        ]);
 
         $client->indices()->stats();
 
-        $connections = $client->getConnections();
-
+        /** @var TraceableSimpleNodePool $nodePool */
+        $nodePool = $client->getTransport()->getNodePool();
+        $nodes = $nodePool->getNodes();
         // two connections are setup
-        $this->assertCount(2, $connections);
+        $this->assertCount(2, $nodes);
 
         // One connection has to be disabled
-        $this->assertTrue(false === $connections[0]->isEnabled() || false === $connections[1]->isEnabled());
+        $this->assertTrue(false === $nodes[0]->isAlive() || false === $nodes[1]->isAlive());
     }
 
     public function testTwoInvalidConnection(): void
     {
-        $client = $this->_getClient();
-
-        $httpClientOptions = [
-            RequestOptions::TIMEOUT => 1,
-            RequestOptions::CONNECT_TIMEOUT => 1,
-        ];
-
-        $transportConnectionBuilder1 = TransportBuilder::create();
-        $transportConnectionBuilder1->setHosts([$this->_getHost().':9101']);
-        $transportConnectionBuilder1->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder2 = TransportBuilder::create();
-        $transportConnectionBuilder2->setHosts([$this->_getHost().':9102']);
-        $transportConnectionBuilder2->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        // First connection work, second should not work
-        $connection1 = new Connection(['host' => $this->_getHost(), 'port' => '9101', 'timeout' => 2, 'transport' => $transportConnectionBuilder1->build()]);
-        $connection2 = new Connection(['host' => $this->_getHost(), 'port' => '9102', 'timeout' => 2, 'transport' => $transportConnectionBuilder2->build()]);
-
-        $client->setConnections([$connection1, $connection2]);
+        $client = $this->_getClient([
+            'hosts' => [
+                // First connection works, second should not work
+                $this->_getHost().':9101',
+                $this->_getHost().':9102',
+            ],
+            'transport_config' => [
+                'http_client_options' => [
+                    RequestOptions::TIMEOUT => 1,
+                    RequestOptions::CONNECT_TIMEOUT => 1,
+                ],
+            ],
+        ]);
 
         try {
             $client->indices()->stats();
             $this->fail('Should throw exception as no connection valid');
-        } catch (NoNodeAvailableException $e) {
+        } catch (NoNodeAvailableException) {
         }
 
-        $connections = $client->getConnections();
+        /** @var TraceableSimpleNodePool $nodePool */
+        $nodePool = $client->getTransport()->getNodePool();
+        $nodes = $nodePool->getNodes();
 
         // two connections are setup
-        $this->assertCount(2, $connections);
+        $this->assertCount(2, $nodes);
 
         // One connection has to be disabled
-        $this->assertTrue(false === $connections[0]->isEnabled() && false === $connections[1]->isEnabled());
-    }
-
-    /**
-     * Tests if the callback works in case a connection is down.
-     */
-    public function testCallback(): void
-    {
-        $count = 0;
-
-        $httpClientOptions = [
-            RequestOptions::TIMEOUT => 1,
-            RequestOptions::CONNECT_TIMEOUT => 1,
-        ];
-
-        $transportConnectionBuilder1 = TransportBuilder::create();
-        $transportConnectionBuilder1->setHosts([$this->_getHost().':9101']);
-        $transportConnectionBuilder1->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder2 = TransportBuilder::create();
-        $transportConnectionBuilder2->setHosts([$this->_getHost().':9102']);
-        $transportConnectionBuilder2->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        // Callback function which verifies that disabled connection objects are returned
-        $callback = function (Connection $connection, \Exception $exception, Client $client) use (&$count): void {
-            $this->assertInstanceOf(Connection::class, $connection);
-            $this->assertInstanceOf(NoNodeAvailableException::class, $exception);
-            $this->assertInstanceOf(Client::class, $client);
-            $this->assertFalse($connection->isEnabled());
-            ++$count;
-        };
-
-        $client = $this->_getClient([], $callback);
-
-        // First connection work, second should not work
-        $connection1 = new Connection(['port' => '9101', 'timeout' => 2, 'transport' => $transportConnectionBuilder1->build()]);
-        $connection2 = new Connection(['port' => '9102', 'timeout' => 2, 'transport' => $transportConnectionBuilder2->build()]);
-
-        $client->setConnections([$connection1, $connection2]);
-
-        $this->assertEquals(0, $count);
-
-        try {
-            $client->indices()->stats();
-            $this->fail('Should throw exception as no connection valid');
-        } catch (NoNodeAvailableException $e) {
-            $this->assertTrue(true);
-        }
-
-        // Two disabled connections (from closure call)
-        $this->assertEquals(2, $count);
-    }
-
-    public function testUrlConstructor(): void
-    {
-        $url = 'http://'.$this->_getHost().':9200/';
-
-        // Url should overwrite invalid host
-        $client = $this->_getClient(['url' => $url, 'port' => '9101', 'timeout' => 2]);
-
-        $response = $client->toElasticaResponse($client->indices()->stats());
-
-        $this->assertTrue($response->isOk());
+        $this->assertTrue(false === $nodes[0]->isAlive() && false === $nodes[1]->isAlive());
     }
 
     public function testUpdateDocumentByDocument(): void
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index 2d2685335d..f7ac859294 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -2,9 +2,8 @@
 
 namespace Elastica\Test;
 
-use Elastic\Transport\Transport;
 use Elastica\Client;
-use Elastica\Connection;
+use Elastica\ClientConfiguration;
 use Elastica\Exception\InvalidException;
 use Elastica\Test\Base as BaseTest;
 
@@ -15,59 +14,44 @@
  */
 class ClientTest extends BaseTest
 {
-    public function testConstruct(): void
+    public function testItConstruct(): void
     {
-        $client = $this->_getClient();
-        $this->assertCount(1, $client->getConnections());
-    }
-
-    public function testConstructWithDsn(): void
-    {
-        $client = new Client('https://user:p4ss@foo.com:9200?retryOnConflict=2');
-        $this->assertCount(1, $client->getConnections());
+        $client = new Client();
 
         $expected = [
-            'host' => 'foo.com',
-            'port' => 9200,
-            'path' => null,
-            'url' => null,
-            'connections' => [],
-            'roundRobin' => false,
-            'retryOnConflict' => 2,
-            'username' => 'user',
-            'password' => 'p4ss',
-            'connectionStrategy' => 'Simple',
+            'hosts' => [ClientConfiguration::DEFAULT_HOST],
+            'retryOnConflict' => 0,
+            'username' => null,
+            'password' => null,
             'transport_config' => [],
         ];
 
         $this->assertEquals($expected, $client->getConfig());
     }
 
-    public function testConnectionParamsArePreparedForConnectionsOption(): void
+    public function testItConstructWithStringAsConfig(): void
     {
-        $url = 'https://'.$this->_getHost().':9200';
-        $client = $this->_getClient(['connections' => [['url' => $url]]]);
-        $connection = $client->getConnection();
-
-        $this->assertEquals($url, $connection->getConfig('url'));
-    }
+        $client = new Client('https://user:p4ss@foo.com:9200?retryOnConflict=2');
 
-    public function testConnectionParamsArePreparedForServersOption(): void
-    {
-        $url = 'https://'.$this->_getHost().':9200';
-        $client = $this->_getClient(['servers' => [['url' => $url]]]);
-        $connection = $client->getConnection();
+        $expected = [
+            'hosts' => ['https://user:p4ss@foo.com:9200?retryOnConflict=2'],
+            'retryOnConflict' => 0,
+            'username' => null,
+            'password' => null,
+            'transport_config' => [],
+        ];
 
-        $this->assertEquals($url, $connection->getConfig('url'));
+        $this->assertEquals($expected, $client->getConfig());
     }
 
-    public function testConnectionParamsArePreparedForDefaultOptions(): void
+    public function testItAddsHosts(): void
     {
-        $url = 'https://'.$this->_getHost().':9200';
-        $client = $this->_getClient(['url' => $url]);
-        $connection = $client->getConnection();
+        $hosts = ['https://my-host.com:9300'];
 
-        $this->assertEquals($url, $connection->getConfig('url'));
+        $client = new Client(['hosts' => $hosts]);
+
+        $this->assertEquals($hosts, $client->getConfig('hosts'));
+        $this->assertEquals('https://my-host.com:9300', $client->getTransport()->getNodePool()->nextNode()->getUri());
     }
 
     public function testAddDocumentsEmpty(): void
@@ -89,7 +73,7 @@ public function testConfigValue(): void
             ],
             'level11' => 'value11',
         ];
-        $client = $this->_getClient($config);
+        $client = new Client($config);
 
         $this->assertNull($client->getConfigValue('level12'));
         $this->assertFalse($client->getConfigValue('level12', false));
@@ -104,45 +88,11 @@ public function testConfigValue(): void
         $this->assertIsArray($client->getConfigValue(['level1', 'level2']));
     }
 
-    public function testAddHeader(): void
-    {
-        $client = $this->_getClient();
-
-        $client->addHeader('foo', 'bar');
-        $this->assertEquals(['foo' => 'bar'], $client->getConfigValue('headers'));
-    }
-
-    public function testRemoveHeader(): void
-    {
-        $client = $this->_getClient();
-
-        $client->addHeader('first', 'first value');
-        $client->addHeader('second', 'second value');
-
-        $client->removeHeader('second');
-        $this->assertEquals(['first' => 'first value'], $client->getConfigValue('headers'));
-    }
-
     public function testPassBigIntSettingsToConnectionConfig(): void
     {
         $client = new Client(['bigintConversion' => true]);
 
-        $this->assertTrue($client->getConnection()->getConfig('bigintConversion'));
-    }
-
-    public function testClientConnectWithConfigSetByMethod(): void
-    {
-        $client = new Client();
-        $client->setConfigValue('host', $this->_getHost());
-        $client->setConfigValue('port', $this->_getPort());
-
-        $client->connect();
-        $this->assertTrue($client->hasConnection());
-
-        $connection = $client->getConnection();
-        $this->assertInstanceOf(Connection::class, $connection);
-        $this->assertEquals($this->_getHost(), $connection->getHost());
-        $this->assertEquals($this->_getPort(), $connection->getPort());
+        $this->assertTrue($client->getConfig('bigintConversion'));
     }
 
     public function testGetAsync(): void
@@ -150,33 +100,24 @@ public function testGetAsync(): void
         $this->expectException(\Exception::class);
         $this->expectExceptionMessage('Not supported');
 
-        $client = $this->_getClient();
+        $client = new Client();
         $client->getAsync();
     }
 
     public function testSetElasticMetaHeader(): void
     {
-        $client = $this->_getClient();
+        $client = new Client();
         $client->setElasticMetaHeader(true);
 
         $this->assertTrue($client->getElasticMetaHeader());
     }
 
-    public function testGetTransport(): void
-    {
-        $this->expectException(\Exception::class);
-        $this->expectExceptionMessage('Not supported');
-
-        $client = $this->_getClient();
-        $client->getTransport();
-    }
-
     public function testSetAsync(): void
     {
         $this->expectException(\Exception::class);
         $this->expectExceptionMessage('Not supported');
 
-        $client = $this->_getClient();
+        $client = new Client();
         $client->setAsync(true);
     }
 
@@ -185,7 +126,7 @@ public function testSetResponseException(): void
         $this->expectException(\Exception::class);
         $this->expectExceptionMessage('Not supported');
 
-        $client = $this->_getClient();
+        $client = new Client();
         $client->setResponseException(true);
     }
 
@@ -194,30 +135,43 @@ public function testGetResponseException(): void
         $this->expectException(\Exception::class);
         $this->expectExceptionMessage('Not supported');
 
-        $client = $this->_getClient();
+        $client = new Client();
         $client->getResponseException();
     }
 
     public function testClientConnectionWithCloudId(): void
     {
         $client = new Client([
-            'host' => 'foo.com',
-            'port' => 9200,
-            'path' => null,
-            'url' => null,
+            'hosts' => ['foo.com:9200'],
             'cloud_id' => 'Test:ZXUtY2VudHJhbC0xLmF3cy5jbG91ZC5lcy5pbyQ0ZGU0NmNlZDhkOGQ0NTk2OTZlNTQ0ZmU1ZjMyYjk5OSRlY2I0YTJlZmY0OTA0ZDliOTE5NzMzMmQwOWNjOTY5Ng==',
-            'connections' => [],
-            'roundRobin' => false,
             'retryOnConflict' => 2,
             'username' => 'user',
             'password' => 'p4ss',
-            'connectionStrategy' => 'Simple',
             'transport_config' => [],
         ]);
-        $transport = $client->getConnection()->getTransportObject();
-        $node = $transport->getNodePool()->nextNode();
 
-        $this->assertInstanceOf(Transport::class, $transport);
+        $node = $client->getTransport()->getNodePool()->nextNode();
+
         $this->assertEquals('4de46ced8d8d459696e544fe5f32b999.eu-central-1.aws.cloud.es.io', $node->getUri()->getHost());
     }
+
+    public function testItThrowsAnExceptionWhenApiKeyAndUserNameInConfigAtTheSameTime(): void
+    {
+        $this->expectException(InvalidException::class);
+        $this->expectExceptionMessage('You cannot use APIKey and Basic Authentication together.');
+
+        new Client([
+            'username' => 'user',
+            'api_key' => 'key',
+        ]);
+    }
+
+    public function testItSetsAuthorizationHeaderIfApiKeyPassed(): void
+    {
+        $apiKey = 'key';
+
+        $client = new Client(['api_key' => $apiKey]);
+
+        self::assertSame(['Authorization' => \sprintf('ApiKey %s', $apiKey)], $client->getTransport()->getHeaders());
+    }
 }
diff --git a/tests/Connection/ConnectionPoolTest.php b/tests/Connection/ConnectionPoolTest.php
deleted file mode 100644
index 65ba8de4a5..0000000000
--- a/tests/Connection/ConnectionPoolTest.php
+++ /dev/null
@@ -1,99 +0,0 @@
-<?php
-
-namespace Elastica\Test\Connection;
-
-use Elastica\Connection;
-use Elastica\Connection\ConnectionPool;
-use Elastica\Connection\Strategy\StrategyFactory;
-use Elastica\Test\Base as BaseTest;
-
-/**
- * @author chabior
- *
- * @internal
- */
-class ConnectionPoolTest extends BaseTest
-{
-    /**
-     * @group unit
-     */
-    public function testConstruct(): void
-    {
-        $pool = $this->createPool();
-
-        $this->assertEquals($this->getConnections(), $pool->getConnections());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testSetConnections(): void
-    {
-        $pool = $this->createPool();
-
-        $connections = $this->getConnections(5);
-
-        $pool->setConnections($connections);
-
-        $this->assertSame($connections, $pool->getConnections());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testAddConnection(): void
-    {
-        $pool = $this->createPool();
-        $pool->setConnections([]);
-
-        $connections = $this->getConnections(5);
-
-        foreach ($connections as $connection) {
-            $pool->addConnection($connection);
-        }
-
-        $this->assertSame($connections, $pool->getConnections());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testHasConnection(): void
-    {
-        $pool = $this->createPool();
-
-        $this->assertTrue($pool->hasConnection());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testFailHasConnections(): void
-    {
-        $pool = $this->createPool();
-
-        $pool->setConnections([]);
-
-        $this->assertFalse($pool->hasConnection());
-    }
-
-    protected function getConnections(int $quantity = 1): array
-    {
-        $params = [];
-        $connections = [];
-
-        for ($i = 0; $i < $quantity; ++$i) {
-            $connections[] = new Connection($params);
-        }
-
-        return $connections;
-    }
-
-    protected function createPool(): ConnectionPool
-    {
-        $connections = $this->getConnections();
-        $strategy = StrategyFactory::create('Simple');
-
-        return new ConnectionPool($connections, $strategy);
-    }
-}
diff --git a/tests/Connection/Strategy/CallbackStrategyTest.php b/tests/Connection/Strategy/CallbackStrategyTest.php
deleted file mode 100644
index 3690bb7f47..0000000000
--- a/tests/Connection/Strategy/CallbackStrategyTest.php
+++ /dev/null
@@ -1,62 +0,0 @@
-<?php
-
-namespace Elastica\Test\Connection\Strategy;
-
-use Elastica\Connection;
-use Elastica\Connection\Strategy\CallbackStrategy;
-use Elastica\Test\Base;
-
-/**
- * Description of CallbackStrategyTest.
- *
- * @author chabior
- *
- * @internal
- */
-class CallbackStrategyTest extends Base
-{
-    /**
-     * @group unit
-     */
-    public function testInvoke(): void
-    {
-        $count = 0;
-
-        $callback = static function ($connections) use (&$count): Connection {
-            ++$count;
-
-            return \current($connections);
-        };
-
-        $mock = $this->createMock(Connection::class);
-        $strategy = new CallbackStrategy($callback);
-        $strategy->getConnection([$mock]);
-
-        $this->assertEquals(1, $count);
-    }
-
-    /**
-     * @group functional
-     */
-    public function testConnection(): void
-    {
-        $count = 0;
-
-        $config = ['connectionStrategy' => static function ($connections) use (&$count): Connection {
-            ++$count;
-
-            return \current($connections);
-        }];
-
-        $client = $this->_getClient($config);
-        $response = $client->toElasticaResponse($client->indices()->getAlias());
-
-        $this->assertEquals(1, $count);
-
-        $this->assertTrue($response->isOk());
-
-        $strategy = $client->getConnectionStrategy();
-
-        $this->assertInstanceOf(CallbackStrategy::class, $strategy);
-    }
-}
diff --git a/tests/Connection/Strategy/EmptyStrategy.php b/tests/Connection/Strategy/EmptyStrategy.php
deleted file mode 100644
index 41b20f4653..0000000000
--- a/tests/Connection/Strategy/EmptyStrategy.php
+++ /dev/null
@@ -1,22 +0,0 @@
-<?php
-
-namespace Elastica\Test\Connection\Strategy;
-
-use Elastica\Connection;
-use Elastica\Connection\Strategy\StrategyInterface;
-
-/**
- * Description of EmptyStrategy.
- *
- * @author chabior
- */
-class EmptyStrategy implements StrategyInterface
-{
-    /**
-     * {@inheritdoc}
-     */
-    public function getConnection(array $connections): Connection
-    {
-        return new Connection();
-    }
-}
diff --git a/tests/Connection/Strategy/RoundRobinTest.php b/tests/Connection/Strategy/RoundRobinTest.php
deleted file mode 100644
index 64e7c0f61f..0000000000
--- a/tests/Connection/Strategy/RoundRobinTest.php
+++ /dev/null
@@ -1,214 +0,0 @@
-<?php
-
-namespace Elastica\Test\Connection\Strategy;
-
-use Elastic\Elasticsearch\Response\Elasticsearch;
-use Elastic\Elasticsearch\Transport\Adapter\AdapterOptions;
-use Elastic\Transport\Exception\NoNodeAvailableException;
-use Elastic\Transport\TransportBuilder;
-use Elastica\Client;
-use Elastica\Connection;
-use Elastica\Connection\Strategy\RoundRobin;
-use Elastica\ResponseConverter;
-use Elastica\Test\Base;
-use GuzzleHttp\RequestOptions;
-use Psr\Http\Client\ClientInterface as HttpClientInterface;
-
-/**
- * Description of RoundRobinTest.
- *
- * @author chabior
- *
- * @internal
- */
-class RoundRobinTest extends Base
-{
-    /**
-     * @var int Number of seconds to wait before timeout is called. Is set low for tests to have fast tests.
-     */
-    protected $_timeout = 1;
-
-    /**
-     * @group functional
-     */
-    public function testConnection(): void
-    {
-        $config = ['connectionStrategy' => 'RoundRobin'];
-        $client = $this->_getClient($config);
-        $response = $client->indices()->getAlias();
-
-        $this->_checkResponse($response);
-
-        $this->_checkStrategy($client);
-    }
-
-    /**
-     * @group unit
-     */
-    public function testOldStrategySet(): void
-    {
-        $config = ['roundRobin' => true];
-        $client = $this->_getClient($config);
-
-        $this->_checkStrategy($client);
-    }
-
-    /**
-     * @group functional
-     */
-    public function testFailConnection(): void
-    {
-        $this->expectException(NoNodeAvailableException::class);
-
-        $config = [
-            'connectionStrategy' => 'RoundRobin',
-            'host' => '255.255.255.0',
-            'timeout' => $this->_timeout,
-            'transport_config' => [
-                'http_client_options' => [
-                    RequestOptions::TIMEOUT => 1,
-                    RequestOptions::CONNECT_TIMEOUT => 1,
-                ],
-            ],
-        ];
-        $client = $this->_getClient($config);
-
-        $this->_checkStrategy($client);
-
-        $client->indices()->getAlias();
-    }
-
-    /**
-     * @group functional
-     */
-    public function testWithOneFailConnection(): void
-    {
-        $httpClientOptions = [
-            RequestOptions::TIMEOUT => 1,
-            RequestOptions::CONNECT_TIMEOUT => 1,
-        ];
-
-        $transportConnectionBuilder1 = TransportBuilder::create();
-        $transportConnectionBuilder1->setHosts(['255.255.255.0']);
-        $transportConnectionBuilder1->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder2 = TransportBuilder::create();
-        $transportConnectionBuilder2->setHosts([$this->_getHost().':'.$this->_getPort()]);
-        $transportConnectionBuilder2->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $connections = [
-            new Connection(['host' => '255.255.255.0', 'timeout' => $this->_timeout, 'transport' => $transportConnectionBuilder1->build()]),
-            new Connection(['host' => $this->_getHost(), 'timeout' => $this->_timeout, 'transport' => $transportConnectionBuilder2->build()]),
-        ];
-
-        $count = 0;
-        $callback = static function ($connection, $exception, $client) use (&$count): void {
-            ++$count;
-        };
-
-        $client = $this->_getClient(['connectionStrategy' => 'RoundRobin'], $callback);
-        $client->setConnections($connections);
-
-        $response = $client->indices()->getAlias();
-
-        $this->_checkResponse($response);
-
-        $this->_checkStrategy($client);
-
-        $this->assertLessThan(\count($connections), $count);
-    }
-
-    /**
-     * @group functional
-     */
-    public function testWithNoValidConnection(): void
-    {
-        $httpClientOptions = [
-            RequestOptions::TIMEOUT => 1,
-            RequestOptions::CONNECT_TIMEOUT => 1,
-        ];
-
-        $transportConnectionBuilder1 = TransportBuilder::create();
-        $transportConnectionBuilder1->setHosts(['255.255.255.0']);
-        $transportConnectionBuilder1->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder2 = TransportBuilder::create();
-        $transportConnectionBuilder2->setHosts(['45.45.45.45:80']);
-        $transportConnectionBuilder2->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder3 = TransportBuilder::create();
-        $transportConnectionBuilder3->setHosts(['10.123.213.123']);
-        $transportConnectionBuilder3->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $connections = [
-            new Connection([
-                'host' => '255.255.255.0',
-                'timeout' => $this->_timeout,
-                'transport' => $transportConnectionBuilder1->build(),
-            ]),
-            new Connection([
-                'host' => '45.45.45.45',
-                'port' => '80',
-                'timeout' => $this->_timeout,
-                'transport' => $transportConnectionBuilder2->build(),
-            ]),
-            new Connection([
-                'host' => '10.123.213.123',
-                'timeout' => $this->_timeout,
-                'transport' => $transportConnectionBuilder3->build(),
-            ]),
-        ];
-
-        $count = 0;
-        $client = $this->_getClient(['roundRobin' => true], static function () use (&$count): void {
-            ++$count;
-        });
-
-        $client->setConnections($connections);
-
-        try {
-            $client->indices()->getAlias();
-            $this->fail('Should throw exception as no connection valid');
-        } catch (NoNodeAvailableException $e) {
-            $this->assertEquals(\count($connections), $count);
-            $this->_checkStrategy($client);
-        }
-    }
-
-    protected function _checkStrategy(Client $client): void
-    {
-        $strategy = $client->getConnectionStrategy();
-
-        $this->assertInstanceOf(RoundRobin::class, $strategy);
-    }
-
-    protected function _checkResponse(Elasticsearch $response): void
-    {
-        $responseElastica = ResponseConverter::toElastica($response);
-
-        $this->assertTrue($responseElastica->isOk());
-    }
-
-    protected function setHttpClientOptions(HttpClientInterface $client, array $config, array $clientOptions = []): HttpClientInterface
-    {
-        if (empty($config) && empty($clientOptions)) {
-            return $client;
-        }
-        $class = \get_class($client);
-        $adapterClass = AdapterOptions::HTTP_ADAPTERS[$class];
-
-        $adapter = new $adapterClass();
-
-        return $adapter->setConfig($client, $config, $clientOptions);
-    }
-}
diff --git a/tests/Connection/Strategy/SimpleTest.php b/tests/Connection/Strategy/SimpleTest.php
deleted file mode 100644
index c93e89adbe..0000000000
--- a/tests/Connection/Strategy/SimpleTest.php
+++ /dev/null
@@ -1,201 +0,0 @@
-<?php
-
-namespace Elastica\Test\Connection\Strategy;
-
-use Elastic\Elasticsearch\Response\Elasticsearch;
-use Elastic\Elasticsearch\Transport\Adapter\AdapterOptions;
-use Elastic\Transport\Exception\NoNodeAvailableException;
-use Elastic\Transport\TransportBuilder;
-use Elastica\Client;
-use Elastica\Connection;
-use Elastica\Connection\Strategy\Simple;
-use Elastica\ResponseConverter;
-use Elastica\Test\Base;
-use GuzzleHttp\RequestOptions;
-use Psr\Http\Client\ClientInterface as HttpClientInterface;
-
-/**
- * Description of SimplyTest.
- *
- * @author chabior
- *
- * @internal
- */
-class SimpleTest extends Base
-{
-    /**
-     * @var int Number of seconds to wait before timeout is called. Is set low for tests to have fast tests.
-     */
-    protected $_timeout = 1;
-
-    /**
-     * @group functional
-     */
-    public function testConnection(): void
-    {
-        $client = $this->_getClient();
-        $response = $client->indices()->getAlias();
-
-        $this->_checkResponse($response);
-
-        $this->_checkStrategy($client);
-    }
-
-    /**
-     * @group functional
-     */
-    public function testFailConnection(): void
-    {
-        $this->expectException(NoNodeAvailableException::class);
-
-        $config = [
-            'connectionStrategy' => 'RoundRobin',
-            'host' => '255.255.255.0',
-            'timeout' => $this->_timeout,
-            'transport_config' => [
-                'http_client_options' => [
-                    RequestOptions::TIMEOUT => 1,
-                    RequestOptions::CONNECT_TIMEOUT => 1,
-                ],
-            ],
-        ];
-        $client = $this->_getClient($config);
-
-        $this->_checkStrategy($client);
-
-        $client->indices()->getAlias();
-    }
-
-    /**
-     * @group functional
-     */
-    public function testWithOneFailConnection(): void
-    {
-        $httpClientOptions = [
-            RequestOptions::TIMEOUT => 1,
-            RequestOptions::CONNECT_TIMEOUT => 1,
-        ];
-
-        $transportConnectionBuilder1 = TransportBuilder::create();
-        $transportConnectionBuilder1->setHosts(['255.255.255.0']);
-        $transportConnectionBuilder1->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder2 = TransportBuilder::create();
-        $transportConnectionBuilder2->setHosts([$this->_getHost().':'.$this->_getPort()]);
-        $transportConnectionBuilder2->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $connections = [
-            new Connection(['host' => '255.255.255.0', 'timeout' => $this->_timeout, 'transport' => $transportConnectionBuilder1->build()]),
-            new Connection(['host' => $this->_getHost(), 'timeout' => $this->_timeout, 'transport' => $transportConnectionBuilder2->build()]),
-        ];
-
-        $count = 0;
-        $callback = static function ($connection, $exception, $client) use (&$count): void {
-            ++$count;
-        };
-
-        $client = $this->_getClient([], $callback);
-        $client->setConnections($connections);
-
-        $response = $client->indices()->getAlias();
-
-        $this->_checkResponse($response);
-
-        $this->_checkStrategy($client);
-
-        $this->assertLessThan(\count($connections), $count);
-    }
-
-    /**
-     * @group functional
-     */
-    public function testWithNoValidConnection(): void
-    {
-        $httpClientOptions = [
-            RequestOptions::TIMEOUT => 1,
-            RequestOptions::CONNECT_TIMEOUT => 1,
-        ];
-
-        $transportConnectionBuilder1 = TransportBuilder::create();
-        $transportConnectionBuilder1->setHosts(['255.255.255.0']);
-        $transportConnectionBuilder1->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder2 = TransportBuilder::create();
-        $transportConnectionBuilder2->setHosts(['45.45.45.45:80']);
-        $transportConnectionBuilder2->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $transportConnectionBuilder3 = TransportBuilder::create();
-        $transportConnectionBuilder3->setHosts(['10.123.213.123']);
-        $transportConnectionBuilder3->setClient(
-            $this->setHttpClientOptions($transportConnectionBuilder1->getClient(), [], $httpClientOptions)
-        );
-
-        $connections = [
-            new Connection([
-                'host' => '255.255.255.0',
-                'timeout' => $this->_timeout,
-                'transport' => $transportConnectionBuilder1->build(),
-            ]),
-            new Connection([
-                'host' => '45.45.45.45',
-                'port' => '80',
-                'timeout' => $this->_timeout,
-                'transport' => $transportConnectionBuilder2->build(),
-            ]),
-            new Connection([
-                'host' => '10.123.213.123',
-                'timeout' => $this->_timeout,
-                'transport' => $transportConnectionBuilder3->build(),
-            ]),
-        ];
-
-        $count = 0;
-        $client = $this->_getClient([], static function () use (&$count): void {
-            ++$count;
-        });
-
-        $client->setConnections($connections);
-
-        try {
-            $client->indices()->getAlias();
-            $this->fail('Should throw exception as no connection valid');
-        } catch (NoNodeAvailableException $e) {
-            $this->assertEquals(\count($connections), $count);
-        }
-    }
-
-    protected function _checkStrategy(Client $client): void
-    {
-        $strategy = $client->getConnectionStrategy();
-
-        $this->assertInstanceOf(Simple::class, $strategy);
-    }
-
-    protected function _checkResponse(Elasticsearch $response): void
-    {
-        $responseElastica = ResponseConverter::toElastica($response);
-
-        $this->assertTrue($responseElastica->isOk());
-    }
-
-    protected function setHttpClientOptions(HttpClientInterface $client, array $config, array $clientOptions = []): HttpClientInterface
-    {
-        if (empty($config) && empty($clientOptions)) {
-            return $client;
-        }
-        $class = \get_class($client);
-        $adapterClass = AdapterOptions::HTTP_ADAPTERS[$class];
-
-        $adapter = new $adapterClass();
-
-        return $adapter->setConfig($client, $config, $clientOptions);
-    }
-}
diff --git a/tests/Connection/Strategy/StrategyFactoryTest.php b/tests/Connection/Strategy/StrategyFactoryTest.php
deleted file mode 100644
index af96ebf5e2..0000000000
--- a/tests/Connection/Strategy/StrategyFactoryTest.php
+++ /dev/null
@@ -1,89 +0,0 @@
-<?php
-
-namespace Elastica\Test\Connection\Strategy;
-
-use Elastica\Connection\Strategy\CallbackStrategy;
-use Elastica\Connection\Strategy\Simple;
-use Elastica\Connection\Strategy\StrategyFactory;
-use Elastica\Test\Base;
-use Elastica\Util;
-
-/**
- * Description of StrategyFactoryTest.
- *
- * @author chabior
- *
- * @internal
- */
-class StrategyFactoryTest extends Base
-{
-    /**
-     * @group unit
-     */
-    public function testCreateCallbackStrategy(): void
-    {
-        $callback = static function ($connections): void {
-        };
-
-        $strategy = StrategyFactory::create($callback);
-
-        $this->assertInstanceOf(CallbackStrategy::class, $strategy);
-    }
-
-    /**
-     * @group unit
-     */
-    public function testCreateByName(): void
-    {
-        $strategyName = 'Simple';
-
-        $strategy = StrategyFactory::create($strategyName);
-
-        $this->assertInstanceOf(Simple::class, $strategy);
-    }
-
-    /**
-     * @group unit
-     */
-    public function testCreateByClass(): void
-    {
-        $strategy = new EmptyStrategy();
-
-        $this->assertEquals($strategy, StrategyFactory::create($strategy));
-    }
-
-    /**
-     * @group unit
-     */
-    public function testCreateByClassName(): void
-    {
-        $strategy = StrategyFactory::create(EmptyStrategy::class);
-
-        $this->assertInstanceOf(EmptyStrategy::class, $strategy);
-    }
-
-    /**
-     * @group unit
-     */
-    public function testFailCreate(): void
-    {
-        $this->expectException(\InvalidArgumentException::class);
-
-        $strategy = new \stdClass();
-
-        StrategyFactory::create($strategy);
-    }
-
-    /**
-     * @group unit
-     */
-    public function testNoCollisionWithGlobalNamespace(): void
-    {
-        // create collision
-        if (!\class_exists('Simple')) {
-            \class_alias(Util::class, 'Simple');
-        }
-        $strategy = StrategyFactory::create('Simple');
-        $this->assertInstanceOf(Simple::class, $strategy);
-    }
-}
diff --git a/tests/ConnectionTest.php b/tests/ConnectionTest.php
deleted file mode 100644
index c4fdfb7003..0000000000
--- a/tests/ConnectionTest.php
+++ /dev/null
@@ -1,215 +0,0 @@
-<?php
-
-namespace Elastica\Test;
-
-use Elastic\Transport\Transport;
-use Elastic\Transport\TransportBuilder;
-use Elastica\Client;
-use Elastica\Connection;
-use Elastica\Exception\InvalidException;
-use Elastica\Test\Base as BaseTest;
-
-/**
- * @internal
- */
-class ConnectionTest extends BaseTest
-{
-    /**
-     * @group unit
-     */
-    public function testEmptyConstructor(): void
-    {
-        $connection = new Connection();
-        $this->assertEquals(Connection::DEFAULT_HOST, $connection->getHost());
-        $this->assertEquals(Connection::DEFAULT_PORT, $connection->getPort());
-        $this->assertEquals([], $connection->getConfig());
-        $this->assertTrue($connection->isEnabled());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testEnabledDisable(): void
-    {
-        $connection = new Connection();
-        $this->assertTrue($connection->isEnabled());
-        $connection->setEnabled(false);
-        $this->assertFalse($connection->isEnabled());
-        $connection->setEnabled(true);
-        $this->assertTrue($connection->isEnabled());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testCreate(): void
-    {
-        $connection = Connection::create();
-        $this->assertInstanceOf(Connection::class, $connection);
-
-        $connection = Connection::create([]);
-        $this->assertInstanceOf(Connection::class, $connection);
-
-        $port = 9999;
-        $connection = Connection::create(['port' => $port]);
-        $this->assertInstanceOf(Connection::class, $connection);
-        $this->assertEquals($port, $connection->getPort());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testCreateInvalid(): void
-    {
-        $this->expectException(InvalidException::class);
-
-        Connection::create('test');
-    }
-
-    /**
-     * @group unit
-     */
-    public function testGetConfig(): void
-    {
-        $url = 'test';
-        $connection = new Connection(['config' => ['url' => $url]]);
-        $this->assertTrue($connection->hasConfig('url'));
-        $this->assertEquals($url, $connection->getConfig('url'));
-
-        $connection->setConfig([]);
-        $this->assertFalse($connection->hasConfig('url'));
-
-        $connection->addConfig('url', $url);
-        $this->assertTrue($connection->hasConfig('url'));
-        $this->assertEquals($url, $connection->getConfig('url'));
-    }
-
-    /**
-     * @group unit
-     */
-    public function testGetConfigWithArrayUsedForTransport(): void
-    {
-        $transportConnectionBuilder = TransportBuilder::create();
-        $transportConnectionBuilder->setHosts([$this->_getHost().':9101']);
-
-        $connection = new Connection(['transport' => $transportConnectionBuilder->build()]);
-        $this->assertInstanceOf(Transport::class, $connection->getTransportObject());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testGetConfigInvalidValue(): void
-    {
-        $this->expectException(InvalidException::class);
-
-        $connection = new Connection();
-        $connection->getConfig('url');
-    }
-
-    /**
-     * @group unit
-     */
-    public function testCompression(): void
-    {
-        $connection = new Connection();
-
-        $this->assertFalse($connection->hasCompression());
-        $connection->setCompression(true);
-        $this->assertTrue($connection->hasCompression());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testCompressionDefaultWithClient(): void
-    {
-        $client = new Client();
-        $connection = $client->getConnection();
-        $this->assertFalse($connection->hasCompression());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testCompressionEnabledWithClient(): void
-    {
-        $client = new Client(['connections' => [['compression' => true]]]);
-        $connection = $client->getConnection();
-
-        $this->assertTrue($connection->hasCompression());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testUsernameFromClient(): void
-    {
-        $username = 'foo';
-        $client = new Client(['username' => $username]);
-
-        $this->assertEquals($username, $client->getConnection()->getUsername());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testPasswordFromClient(): void
-    {
-        $password = 'bar';
-        $client = new Client(['password' => $password]);
-
-        $this->assertEquals($password, $client->getConnection()->getPassword());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testPathFromClient(): void
-    {
-        $path = 'test';
-        $client = new Client(['path' => $path]);
-
-        $this->assertEquals($path, $client->getConnection()->getPath());
-
-        $changedPath = 'test2';
-
-        $client->getConnection()->setPath($changedPath);
-
-        $this->assertEquals($changedPath, $client->getConnection()->getPath());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testPortFromClient(): void
-    {
-        $port = 9000;
-        $client = new Client(['port' => $port]);
-
-        $this->assertEquals($port, $client->getConnection()->getPort());
-
-        $changedPort = 9001;
-
-        $client->getConnection()->setPort($changedPort);
-
-        $this->assertEquals($changedPort, $client->getConnection()->getPort());
-    }
-
-    /**
-     * @group unit
-     */
-    public function testHostFromClient(): void
-    {
-        $host = 'localhost';
-        $client = new Client(['host' => $host]);
-
-        $this->assertEquals($host, $client->getConnection()->getHost());
-
-        $changedHost = 'localhostChanged';
-
-        $client->getConnection()->setHost($changedHost);
-
-        $this->assertEquals($changedHost, $client->getConnection()->getHost());
-    }
-}
diff --git a/tests/Transport/NodePool/TraceableSimpleNodePool.php b/tests/Transport/NodePool/TraceableSimpleNodePool.php
new file mode 100644
index 0000000000..5be8c3e5bb
--- /dev/null
+++ b/tests/Transport/NodePool/TraceableSimpleNodePool.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Elastica\Test\Transport\NodePool;
+
+use Elastic\Transport\NodePool\Node;
+use Elastic\Transport\NodePool\SimpleNodePool;
+
+final class TraceableSimpleNodePool extends SimpleNodePool
+{
+    /**
+     * Original method shuffle connections so it's a problem in tests.
+     */
+    public function setHosts(array $hosts): SimpleNodePool
+    {
+        $this->nodes = [];
+        foreach ($hosts as $host) {
+            $this->nodes[] = new Node($host);
+        }
+
+        $this->selector->setNodes($this->nodes);
+
+        return $this;
+    }
+
+    /**
+     * @return array<Node>
+     */
+    public function getNodes(): array
+    {
+        return $this->nodes;
+    }
+}