diff --git a/composer.json b/composer.json
index ff6a859..7a24d7b 100644
--- a/composer.json
+++ b/composer.json
@@ -19,7 +19,8 @@
         "phpstan/phpstan": "^1.10",
         "phpstan/phpstan-symfony": "^1.3",
         "phpunit/phpunit": "^10.5",
-        "rector/rector": "^1.2"
+        "rector/rector": "^1.2",
+        "mikey179/vfsstream": "^1.6"
     },
     "autoload": {
         "psr-4": {
diff --git a/src/Client/JsonRpc/JsonRpcClient.php b/src/Client/JsonRpc/JsonRpcClient.php
new file mode 100644
index 0000000..37c5bfc
--- /dev/null
+++ b/src/Client/JsonRpc/JsonRpcClient.php
@@ -0,0 +1,88 @@
+<?php
+
+namespace Sal\Seven\Client\JsonRpc;
+
+use GuzzleHttp\Exception\GuzzleException;
+use Sal\Seven\Adapter\Http\HttpAdapterInterface;
+use Sal\Seven\Factory\HttpHeaderFactory;
+use Sal\Seven\Model\ContentType;
+use Sal\Seven\Model\JsonRpc\JsonRpcResponse;
+use Symfony\Component\Serializer\Exception\ExceptionInterface;
+use Symfony\Component\Serializer\SerializerInterface;
+
+class JsonRpcClient implements JsonRpcClientInterface
+{
+    private ?string $endpoint = null;
+
+    private mixed $auth = null;
+
+    public function __construct(
+        private readonly SerializerInterface $serializer,
+        private readonly HttpAdapterInterface $http,
+    ) {
+        $this->http->addHeader(HttpHeaderFactory::contentType(ContentType::JSON));
+    }
+
+    public function setEndpoint(string $endpoint): void
+    {
+        $this->endpoint = $endpoint;
+    }
+
+    public function setAuth(mixed $auth): void
+    {
+        $this->auth = $auth;
+    }
+
+    /**
+     * @param mixed[] $params
+     *
+     * @throws GuzzleException
+     * @throws \RuntimeException
+     * @throws ExceptionInterface
+     */
+    public function call(string $method, array $params = []): JsonRpcResponse
+    {
+        if (null === $this->endpoint) {
+            throw new \RuntimeException('The JSON-RPC endpoint not set.');
+        }
+
+        $payload = [
+            'jsonrpc' => '2.0',
+            'method' => $method,
+            'params' => $params,
+            'id' => (string) microtime(),
+            'auth' => $this->auth,
+        ];
+
+        $json = json_encode($payload);
+        if (false === $json) {
+            throw new \RuntimeException('Invalid JSON-RPC payload.');
+        }
+
+        $response = $this->http->post(
+            $this->endpoint,
+            json: $json
+        );
+
+        if (!$response->isSuccessful()) {
+            throw new \RuntimeException("JSON-RPC responded with {$response->getStatusCode()}: '{$response->getBody()?->getContents()}'");
+        }
+
+        $body = $response->getBody()?->getContents();
+        if (null === $body) {
+            throw new \RuntimeException('No JSON-RPC response received.');
+        }
+
+        $response = $this->serializer->deserialize(
+            $body,
+            JsonRpcResponse::class,
+            'json'
+        );
+
+        if (!$response instanceof JsonRpcResponse) {
+            throw new \RuntimeException('Invalid JSON-RPC response.');
+        }
+
+        return $response;
+    }
+}
diff --git a/src/Client/JsonRpc/JsonRpcClientInterface.php b/src/Client/JsonRpc/JsonRpcClientInterface.php
new file mode 100644
index 0000000..f7cbb64
--- /dev/null
+++ b/src/Client/JsonRpc/JsonRpcClientInterface.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Sal\Seven\Client\JsonRpc;
+
+use GuzzleHttp\Exception\GuzzleException;
+use Sal\Seven\Model\JsonRpc\JsonRpcResponse;
+use Symfony\Component\Console\Exception\ExceptionInterface;
+
+interface JsonRpcClientInterface
+{
+    /**
+     * @param mixed[] $params A JSON encodable array of parameters
+     *
+     * @throws GuzzleException
+     * @throws \RuntimeException
+     * @throws ExceptionInterface
+     */
+    public function call(string $method, array $params = []): JsonRpcResponse;
+
+    public function setEndpoint(string $endpoint): void;
+
+    public function setAuth(mixed $auth): void;
+}
diff --git a/src/Model/JsonRpc/JsonRpcError.php b/src/Model/JsonRpc/JsonRpcError.php
new file mode 100644
index 0000000..8b4e02c
--- /dev/null
+++ b/src/Model/JsonRpc/JsonRpcError.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Sal\Seven\Model\JsonRpc;
+
+readonly class JsonRpcError
+{
+    public function __construct(
+        private int $code,
+        private string $message,
+        private mixed $data = null,
+    ) {
+    }
+
+    public function getCode(): int
+    {
+        return $this->code;
+    }
+
+    public function getMessage(): string
+    {
+        return $this->message;
+    }
+
+    public function getData(): mixed
+    {
+        return $this->data;
+    }
+}
diff --git a/src/Model/JsonRpc/JsonRpcResponse.php b/src/Model/JsonRpc/JsonRpcResponse.php
new file mode 100644
index 0000000..b4d75d6
--- /dev/null
+++ b/src/Model/JsonRpc/JsonRpcResponse.php
@@ -0,0 +1,33 @@
+<?php
+
+namespace Sal\Seven\Model\JsonRpc;
+
+class JsonRpcResponse
+{
+    public function __construct(
+        private readonly ?string $id,
+        private readonly mixed $result,
+        private readonly ?JsonRpcError $error = null,
+    ) {
+    }
+
+    public function getId(): ?string
+    {
+        return $this->id;
+    }
+
+    public function getResult(): mixed
+    {
+        return $this->result;
+    }
+
+    public function getError(): ?JsonRpcError
+    {
+        return $this->error;
+    }
+
+    public function isSuccessful(): bool
+    {
+        return null === $this->error;
+    }
+}
diff --git a/tests/Adapter/Ssh/SshAdapterTest.php b/tests/Adapter/Ssh/SshAdapterTest.php
index 2898502..cf827d1 100644
--- a/tests/Adapter/Ssh/SshAdapterTest.php
+++ b/tests/Adapter/Ssh/SshAdapterTest.php
@@ -10,7 +10,7 @@
 
 class SshAdapterTest extends TestCase
 {
-    public function testSetLogger()
+    public function testSetLogger(): void
     {
         $adapter = new SshAdapter();
         /** @var LoggerInterface|MockObject */
@@ -24,7 +24,7 @@ public function testSetLogger()
         $this->assertInstanceOf(NullLogger::class, $adapter->getLogger());
     }
 
-    public function testSetTimeout()
+    public function testSetTimeout(): void
     {
         $adapter = new SshAdapter();
         $adapter->setTimeout(120);
@@ -36,7 +36,7 @@ public function testSetTimeout()
         $this->assertContains('ConnectTimeout=0', $adapter->getOptions());
     }
 
-    public function testSetters()
+    public function testSetters(): void
     {
         $adapter = new SshAdapter();
         $adapter->setHost('127.0.0.1');
@@ -49,7 +49,7 @@ public function testSetters()
         $this->assertContains('-o', $adapter->getOptions());
     }
 
-    public function testAddIdentityFile()
+    public function testAddIdentityFile(): void
     {
         $adapter = new SshAdapter();
         $adapter->addIdentityFile('/path/to/id_rsa');
@@ -57,7 +57,7 @@ public function testAddIdentityFile()
         $this->assertContains('/path/to/id_rsa', $adapter->getOptions());
     }
 
-    public function testAddJump()
+    public function testAddJump(): void
     {
         $adapter = new SshAdapter();
         $adapter->addJump('jump.example.com');
@@ -65,7 +65,7 @@ public function testAddJump()
         $this->assertContains('jump.example.com', $adapter->getOptions());
     }
 
-    public function testAddConfigFile()
+    public function testAddConfigFile(): void
     {
         $adapter = new SshAdapter();
         $adapter->addConfigFile('/path/to/ssh_config');
@@ -73,7 +73,7 @@ public function testAddConfigFile()
         $this->assertContains('/path/to/ssh_config', $adapter->getOptions());
     }
 
-    public function testAddOption()
+    public function testAddOption(): void
     {
         $adapter = new SshAdapter();
         $adapter->addOption('test');
@@ -81,7 +81,7 @@ public function testAddOption()
         $this->assertContains('test', $adapter->getOptions());
     }
 
-    public function testPermitDsaHostKey()
+    public function testPermitDsaHostKey(): void
     {
         $adapter = new SshAdapter();
         $options = $adapter->getOptions();
diff --git a/tests/Client/JsonRpc/JsonRpcClientTest.php b/tests/Client/JsonRpc/JsonRpcClientTest.php
new file mode 100644
index 0000000..04d3442
--- /dev/null
+++ b/tests/Client/JsonRpc/JsonRpcClientTest.php
@@ -0,0 +1,139 @@
+<?php
+
+namespace Sal\Seven\Tests\Client\JsonRpc;
+
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\StreamInterface;
+use Sal\Seven\Adapter\Http\HttpAdapterInterface;
+use Sal\Seven\Client\JsonRpc\JsonRpcClient;
+use Sal\Seven\Factory\HttpHeaderFactory;
+use Sal\Seven\Model\ContentType;
+use Sal\Seven\Model\Http\HttpResponse;
+use Sal\Seven\Model\JsonRpc\JsonRpcResponse;
+use Symfony\Component\Serializer\SerializerInterface;
+
+class JsonRpcClientTest extends TestCase
+{
+    /** @var SerializerInterface|MockObject */
+    private SerializerInterface $serializer;
+
+    /** @var HttpAdapterInterface|MockObject */
+    private HttpAdapterInterface $http;
+
+    private JsonRpcClient $client;
+
+    protected function setUp(): void
+    {
+        $this->serializer = $this->createMock(SerializerInterface::class);
+        $this->http = $this->createMock(HttpAdapterInterface::class);
+
+        $this->http
+            ->expects($this->once())
+            ->method('addHeader')
+            ->with(HttpHeaderFactory::contentType(ContentType::JSON));
+
+        $this->client = new JsonRpcClient($this->serializer, $this->http);
+    }
+
+    public function testThrowsIfEndpointMissing(): void
+    {
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('The JSON-RPC endpoint not set.');
+        $this->client->call('method');
+    }
+
+    public function testThrowsOnInvalidJsonPayload(): void
+    {
+        $this->client->setEndpoint('http://test');
+
+        $this->client->setAuth("\xB1\x31"); // force json_decode to fail
+
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('Invalid JSON-RPC payload.');
+        $this->client->call('method');
+    }
+
+    public function testThrowsIfHttpNotSuccessful(): void
+    {
+        $this->client->setEndpoint('http://test');
+        $this->client->setAuth('auth');
+
+        $stream = $this->createMock(StreamInterface::class);
+        $stream->method('getContents')->willReturn('ERR');
+
+        $httpResponse = $this->createMock(HttpResponse::class);
+        $httpResponse->method('isSuccessful')->willReturn(false);
+        $httpResponse->method('getStatusCode')->willReturn(500);
+        $httpResponse->method('getBody')->willReturn($stream);
+
+        $this->http->method('post')->willReturn($httpResponse);
+
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage("500: 'ERR'");
+
+        $this->client->call('test');
+    }
+
+    public function testThrowsIfNoBody(): void
+    {
+        $this->client->setEndpoint('http://test');
+
+        $httpResponse = $this->createMock(HttpResponse::class);
+        $httpResponse->method('isSuccessful')->willReturn(true);
+        $httpResponse->method('getBody')->willReturn(null);
+
+        $this->http->method('post')->willReturn($httpResponse);
+
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('No JSON-RPC response received.');
+
+        $this->client->call('test');
+    }
+
+    public function testThrowsIfInvalidResponseObject(): void
+    {
+        $this->client->setEndpoint('http://test');
+
+        $stream = $this->createMock(StreamInterface::class);
+        $stream->method('getContents')->willReturn('{"ok":1}');
+
+        $httpResponse = $this->createMock(HttpResponse::class);
+        $httpResponse->method('isSuccessful')->willReturn(true);
+        $httpResponse->method('getBody')->willReturn($stream);
+
+        $this->http->method('post')->willReturn($httpResponse);
+        $this->serializer->method('deserialize')->willReturn(new \stdClass());
+
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('Invalid JSON-RPC response.');
+
+        $this->client->call('test');
+    }
+
+    public function testSuccessfulCall(): void
+    {
+        $this->client->setEndpoint('http://test');
+        $this->client->setAuth('auth');
+
+        $stream = $this->createMock(StreamInterface::class);
+        $stream->method('getContents')->willReturn('{"result":123}');
+
+        $httpResponse = $this->createMock(HttpResponse::class);
+        $httpResponse->method('isSuccessful')->willReturn(true);
+        $httpResponse->method('getBody')->willReturn($stream);
+
+        $this->http->method('post')->willReturn($httpResponse);
+
+        $expected = $this->createMock(JsonRpcResponse::class);
+
+        $this->serializer
+            ->method('deserialize')
+            ->with('{"result":123}', JsonRpcResponse::class, 'json')
+            ->willReturn($expected);
+
+        $out = $this->client->call('method', ['a' => 1]);
+
+        $this->assertSame($expected, $out);
+    }
+}
diff --git a/tests/Loader/SshAdapterConfigLoaderTest.php b/tests/Loader/SshAdapterConfigLoaderTest.php
new file mode 100644
index 0000000..0e8dbbd
--- /dev/null
+++ b/tests/Loader/SshAdapterConfigLoaderTest.php
@@ -0,0 +1,75 @@
+<?php
+
+namespace Sal\Seven\Tests\Loader;
+
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+use Sal\Seven\Loader\SshAdapterConfigLoader;
+use Sal\Seven\Model\Config\SshAdapterConfig;
+use Symfony\Component\Serializer\Exception\BadMethodCallException;
+use Symfony\Component\Serializer\SerializerInterface;
+
+class SshAdapterConfigLoaderTest extends TestCase
+{
+    public function testReturnsNullIfFileDoesNotExist(): void
+    {
+        $serializer = $this->createMock(SerializerInterface::class);
+        $logger = $this->createMock(LoggerInterface::class);
+
+        $logger->expects($this->once())
+            ->method('error')
+            ->with($this->stringContains('does not exist'));
+
+        $loader = new SshAdapterConfigLoader(
+            '/nonexistent.yml',
+            $serializer,
+            $logger
+        );
+
+        $this->assertNull($loader->load());
+    }
+
+    public function testReturnsConfigOnSuccessfulDeserialize(): void
+    {
+        $path = tempnam(sys_get_temp_dir(), 't');
+        file_put_contents($path, "options:\n  - a\n");
+
+        $serializer = $this->createMock(SerializerInterface::class);
+
+        $config = new SshAdapterConfig(['a']);
+
+        $serializer->method('deserialize')
+            ->with($this->stringContains('options'), SshAdapterConfig::class, 'yaml')
+            ->willReturn($config);
+
+        $loader = new SshAdapterConfigLoader($path, $serializer);
+
+        $this->assertSame($config, $loader->load());
+
+        unlink($path);
+    }
+
+    public function testReturnsNullOnDeserializeException(): void
+    {
+        $path = tempnam(sys_get_temp_dir(), 't');
+        file_put_contents($path, "broken:\n  - x\n");
+
+        $serializer = $this->createMock(SerializerInterface::class);
+        $logger = $this->createMock(LoggerInterface::class);
+
+        $serializer->method('deserialize')
+            ->willThrowException(
+                new BadMethodCallException()
+            );
+
+        $logger->expects($this->once())
+            ->method('error')
+            ->with($this->stringContains('Unable to deserialize'));
+
+        $loader = new SshAdapterConfigLoader($path, $serializer, $logger);
+
+        $this->assertNull($loader->load());
+
+        unlink($path);
+    }
+}
diff --git a/tests/Model/Config/SshAdapterConfigTest.php b/tests/Model/Config/SshAdapterConfigTest.php
new file mode 100644
index 0000000..d61c741
--- /dev/null
+++ b/tests/Model/Config/SshAdapterConfigTest.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Sal\Seven\Tests\Model\Config;
+
+use PHPUnit\Framework\TestCase;
+use Sal\Seven\Model\Config\SshAdapterConfig;
+
+class SshAdapterConfigTest extends TestCase
+{
+    public function testConstructorAndGetOptions(): void
+    {
+        $config = new SshAdapterConfig(['a', 'b']);
+
+        $this->assertSame(['a', 'b'], $config->getOptions());
+    }
+
+    public function testAddOption(): void
+    {
+        $config = new SshAdapterConfig(['x']);
+
+        $returned = $config->addOption('y');
+
+        $this->assertSame($config, $returned);
+        $this->assertSame(['x', 'y'], $config->getOptions());
+    }
+}
diff --git a/tests/Model/HttpResponseTest.php b/tests/Model/Http/HttpResponseTest.php
similarity index 84%
rename from tests/Model/HttpResponseTest.php
rename to tests/Model/Http/HttpResponseTest.php
index 35b9358..38bc9f3 100644
--- a/tests/Model/HttpResponseTest.php
+++ b/tests/Model/Http/HttpResponseTest.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace Sal\Seven\Tests\Model;
+namespace Sal\Seven\Tests\Model\Http;
 
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
@@ -21,13 +21,13 @@ public function testParseJsonInvalid(): void
         $this->assertNull($response->parseJson());
     }
 
-    public function testGetStatusCode()
+    public function testGetStatusCode(): void
     {
         $response = new HttpResponse(200);
         $this->assertSame(200, $response->getStatusCode());
     }
 
-    public function testGetBody()
+    public function testGetBody(): void
     {
         /** @var StreamInterface|MockObject $stream */
         $stream = $this->createMock(StreamInterface::class);
@@ -35,7 +35,7 @@ public function testGetBody()
         $this->assertSame($stream, $response->getBody());
     }
 
-    public function testIsSuccessful()
+    public function testIsSuccessful(): void
     {
         $response = new HttpResponse(200);
         $this->assertTrue($response->isSuccessful());
@@ -44,7 +44,7 @@ public function testIsSuccessful()
         $this->assertFalse($response->isSuccessful());
     }
 
-    public function testParseJsonReturnsArray()
+    public function testParseJsonReturnsArray(): void
     {
         /** @var StreamInterface|MockObject $stream */
         $stream = $this->createMock(StreamInterface::class);
@@ -54,13 +54,13 @@ public function testParseJsonReturnsArray()
         $this->assertSame(['foo' => 'bar'], $response->parseJson());
     }
 
-    public function testParseJsonReturnsNullIfBodyIsNull()
+    public function testParseJsonReturnsNullIfBodyIsNull(): void
     {
         $response = new HttpResponse(200, null);
         $this->assertNull($response->parseJson());
     }
 
-    public function testParseJsonThrowsExceptionOnInvalidJson()
+    public function testParseJsonThrowsExceptionOnInvalidJson(): void
     {
         $this->expectException(\RuntimeException::class);
         $this->expectExceptionMessage('Invalid JSON response.');
diff --git a/tests/Model/JsonRpc/JsonRpcErrorTest.php b/tests/Model/JsonRpc/JsonRpcErrorTest.php
new file mode 100644
index 0000000..59ccc0e
--- /dev/null
+++ b/tests/Model/JsonRpc/JsonRpcErrorTest.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace Sal\Seven\Tests\Model\JsonRpc;
+
+use PHPUnit\Framework\TestCase;
+use Sal\Seven\Model\JsonRpc\JsonRpcError;
+
+class JsonRpcErrorTest extends TestCase
+{
+    public function testGetters(): void
+    {
+        $error = new JsonRpcError(
+            code: 123,
+            message: 'Something went wrong',
+            data: ['x' => 1]
+        );
+
+        $this->assertSame(123, $error->getCode());
+        $this->assertSame('Something went wrong', $error->getMessage());
+        $this->assertSame(['x' => 1], $error->getData());
+    }
+
+    public function testGettersWithNullData(): void
+    {
+        $error = new JsonRpcError(
+            code: -1,
+            message: 'Error message'
+        );
+
+        $this->assertSame(-1, $error->getCode());
+        $this->assertSame('Error message', $error->getMessage());
+        $this->assertNull($error->getData());
+    }
+}
diff --git a/tests/Model/JsonRpc/JsonRpcResponseTest.php b/tests/Model/JsonRpc/JsonRpcResponseTest.php
new file mode 100644
index 0000000..ee4fbff
--- /dev/null
+++ b/tests/Model/JsonRpc/JsonRpcResponseTest.php
@@ -0,0 +1,43 @@
+<?php
+
+namespace Sal\Seven\Tests\Model\JsonRpc;
+
+use PHPUnit\Framework\TestCase;
+use Sal\Seven\Model\JsonRpc\JsonRpcError;
+use Sal\Seven\Model\JsonRpc\JsonRpcResponse;
+
+class JsonRpcResponseTest extends TestCase
+{
+    public function testSuccessfulResponse(): void
+    {
+        $response = new JsonRpcResponse(
+            id: '123',
+            result: ['ok' => true],
+            error: null
+        );
+
+        $this->assertSame('123', $response->getId());
+        $this->assertSame(['ok' => true], $response->getResult());
+        $this->assertNull($response->getError());
+        $this->assertTrue($response->isSuccessful());
+    }
+
+    public function testErrorResponse(): void
+    {
+        $error = new JsonRpcError(
+            code: -32600,
+            message: 'Invalid request'
+        );
+
+        $response = new JsonRpcResponse(
+            id: null,
+            result: null,
+            error: $error
+        );
+
+        $this->assertNull($response->getId());
+        $this->assertNull($response->getResult());
+        $this->assertSame($error, $response->getError());
+        $this->assertFalse($response->isSuccessful());
+    }
+}