diff --git a/tests/HttpClient/HttpClientTest.php b/tests/HttpClient/HttpClientTest.php
new file mode 100644
index 000000000..f1e4c0660
--- /dev/null
+++ b/tests/HttpClient/HttpClientTest.php
@@ -0,0 +1,97 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\Tests\HttpClient;
+
+use PHPUnit\Framework\TestCase;
+use Sentry\HttpClient\HttpClient;
+use Sentry\HttpClient\Request;
+use Sentry\Options;
+use Sentry\Util\Http;
+
+class HttpClientTest extends TestCase
+{
+    use TestServer;
+
+    public function testClientMakesRequestWithCorrectHeadersMethodAndPath(): void
+    {
+        $testServer = $this->startTestServer();
+
+        $options = new Options([
+            'dsn' => "http://publicKey@{$testServer}/200",
+            'http_compression' => false,
+        ]);
+
+        $request = new Request();
+        $request->setStringBody('test');
+
+        $client = new HttpClient($sdkIdentifier = 'sentry.php', $sdkVersion = 'testing');
+        $response = $client->sendRequest($request, $options);
+
+        $serverOutput = $this->stopTestServer();
+
+        $this->assertTrue($response->isSuccess());
+        $this->assertEquals(200, $response->getStatusCode());
+
+        // This assertion is here to test that the response headers are correctly parsed
+        $this->assertEquals(200, (int) $response->getHeaderLine('x-sentry-test-server-status-code'));
+
+        $this->assertEquals($response->getStatusCode(), $serverOutput['status']);
+        $this->assertEquals($request->getStringBody(), $serverOutput['body']);
+        $this->assertEquals('/api/200/envelope/', $serverOutput['server']['REQUEST_URI']);
+        $this->assertEquals("{$sdkIdentifier}/{$sdkVersion}", $serverOutput['headers']['User-Agent']);
+        $this->assertEquals(\strlen($request->getStringBody()), $serverOutput['headers']['Content-Length']);
+
+        $expectedHeaders = Http::getRequestHeaders($options->getDsn(), $sdkIdentifier, $sdkVersion);
+        foreach ($expectedHeaders as $expectedHeader) {
+            [$headerName, $headerValue] = explode(': ', $expectedHeader);
+            $this->assertEquals($headerValue, $serverOutput['headers'][$headerName]);
+        }
+    }
+
+    public function testClientMakesCompressedRequest(): void
+    {
+        $testServer = $this->startTestServer();
+
+        $options = new Options([
+            'dsn' => "http://publicKey@{$testServer}/200",
+            'http_compression' => true,
+        ]);
+
+        $request = new Request();
+        $request->setStringBody('test');
+
+        $client = new HttpClient('sentry.php', 'testing');
+        $response = $client->sendRequest($request, $options);
+
+        $serverOutput = $this->stopTestServer();
+
+        $this->assertTrue($response->isSuccess());
+        $this->assertEquals(200, $response->getStatusCode());
+        $this->assertEquals($response->getStatusCode(), $serverOutput['status']);
+        $this->assertEquals($request->getStringBody(), $serverOutput['body']);
+    }
+
+    public function testThrowsExceptionIfDsnOptionIsNotSet(): void
+    {
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('The DSN option must be set to use the HttpClient.');
+
+        $options = new Options(['dsn' => null]);
+
+        $client = new HttpClient('sentry.php', 'testing');
+        $client->sendRequest(new Request(), $options);
+    }
+
+    public function testThrowsExceptionIfRequestDataIsEmpty(): void
+    {
+        $this->expectException(\RuntimeException::class);
+        $this->expectExceptionMessage('The request data is empty.');
+
+        $options = new Options(['dsn' => 'https://publicKey@example.com/1']);
+
+        $client = new HttpClient('sentry.php', 'testing');
+        $client->sendRequest(new Request(), $options);
+    }
+}
diff --git a/tests/HttpClient/TestServer.php b/tests/HttpClient/TestServer.php
new file mode 100644
index 000000000..d4884c6a8
--- /dev/null
+++ b/tests/HttpClient/TestServer.php
@@ -0,0 +1,140 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\Tests\HttpClient;
+
+/**
+ * This is a test server that can be used to test the HttpClient.
+ *
+ * It spawns the PHP development server, captures the output and returns it to the caller.
+ *
+ * In your test call `$this->startTestServer()` to start the server and get the address.
+ * After you have made your request, call `$this->stopTestServer()` to stop the server and get the output.
+ *
+ * Thanks to Stripe for the inspiration: https://github.com/stripe/stripe-php/blob/e0a960c8655b21b21c3ba2e5927f432eeda9105f/tests/TestServer.php
+ */
+trait TestServer
+{
+    /**
+     * @var string the path to the output file
+     */
+    protected static $serverOutputFile = __DIR__ . '/../testserver/output.json';
+
+    /**
+     * @var resource|null the server process handle
+     */
+    protected $serverProcess;
+
+    /**
+     * @var resource|null the server stderr handle
+     */
+    protected $serverStderr;
+
+    /**
+     * @var int the port on which the server is listening, this default value was randomly chosen
+     */
+    protected $serverPort = 44884;
+
+    public function startTestServer(): string
+    {
+        if ($this->serverProcess !== null) {
+            throw new \RuntimeException('There is already a test server instance running.');
+        }
+
+        if (file_exists(self::$serverOutputFile)) {
+            unlink(self::$serverOutputFile);
+        }
+
+        $pipes = [];
+
+        $this->serverProcess = proc_open(
+            $command = sprintf(
+                'php -S localhost:%d -t %s',
+                $this->serverPort,
+                __DIR__ . '/../testserver'
+            ),
+            [2 => ['pipe', 'w']],
+            $pipes
+        );
+
+        $this->serverStderr = $pipes[2];
+
+        $pid = proc_get_status($this->serverProcess)['pid'];
+
+        if (!\is_resource($this->serverProcess)) {
+            throw new \RuntimeException("Error starting test server on pid {$pid}, command failed: {$command}");
+        }
+
+        while (true) {
+            $conn = @fsockopen('localhost', $this->serverPort);
+            if (\is_resource($conn)) {
+                fclose($conn);
+
+                break;
+            }
+        }
+
+        return "localhost:{$this->serverPort}";
+    }
+
+    /**
+     * Stop the test server and return the output from the server.
+     *
+     * @return array{
+     *     body: string,
+     *     status: int,
+     *     server: array<string, string>,
+     *     headers: array<string, string>,
+     * }
+     */
+    public function stopTestServer(): array
+    {
+        if (!$this->serverProcess) {
+            throw new \RuntimeException('There is no test server instance running.');
+        }
+
+        for ($i = 0; $i < 20; ++$i) {
+            $status = proc_get_status($this->serverProcess);
+
+            if (!$status['running']) {
+                break;
+            }
+
+            $this->killServerProcess($this->serverProcess);
+
+            usleep(10000);
+        }
+
+        if ($status['running']) {
+            throw new \RuntimeException('Could not kill test server');
+        }
+
+        if (!file_exists(self::$serverOutputFile)) {
+            stream_set_blocking($this->serverStderr, false);
+            $stderrOutput = stream_get_contents($this->serverStderr);
+
+            echo $stderrOutput . \PHP_EOL;
+
+            throw new \RuntimeException('Test server did not write output file');
+        }
+
+        proc_close($this->serverProcess);
+
+        $this->serverProcess = null;
+        $this->serverStderr = null;
+
+        return json_decode(file_get_contents(self::$serverOutputFile), true);
+    }
+
+    private function killServerProcess($process)
+    {
+        if (\PHP_OS_FAMILY === 'Windows') {
+            $status = proc_get_status($process);
+
+            exec("taskkill /pid {$status['pid']} /f /t");
+        } else {
+            proc_terminate($process);
+        }
+    }
+}
diff --git a/tests/testserver/.gitignore b/tests/testserver/.gitignore
new file mode 100644
index 000000000..e102ff534
--- /dev/null
+++ b/tests/testserver/.gitignore
@@ -0,0 +1 @@
+output.json
diff --git a/tests/testserver/index.php b/tests/testserver/index.php
new file mode 100644
index 000000000..ba8fd3da5
--- /dev/null
+++ b/tests/testserver/index.php
@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+$outputFile = __DIR__ . '/output.json';
+
+// We expect the path to be `/api/<project_id>/envelope/`.
+// We use the project ID to determine the status code so we need to extract it from the path
+$path = trim(parse_url($_SERVER['REQUEST_URI'], \PHP_URL_PATH), '/');
+
+if (!preg_match('/api\/\d+\/envelope/', $path)) {
+    http_response_code(204);
+
+    return;
+}
+
+$status = (int) explode('/', $path)[1];
+
+$headers = getallheaders();
+
+$rawBody = file_get_contents('php://input');
+
+if (!isset($headers['Content-Encoding'])) {
+    $body = $rawBody;
+} elseif ($headers['Content-Encoding'] === 'gzip') {
+    $body = gzdecode($rawBody);
+} else {
+    $body = '__unable to decode body__';
+}
+
+$output = [
+    'body' => $body,
+    'status' => $status,
+    'server' => $_SERVER,
+    'headers' => $headers,
+];
+
+file_put_contents(__DIR__ . '/output.json', json_encode($output, \JSON_PRETTY_PRINT));
+
+header('X-Sentry-Test-Server-Status-Code: ' . $status);
+
+http_response_code($status);
+
+return 'Processed.';