fix: let the Docker daemon allocate host ports by default

src/Container/GenericContainer.php

@@ -19,7 +19,6 @@
 use RuntimeException;
 use Testcontainers\ContainerClient\DockerContainerClient;
 use Testcontainers\Utils\PortGenerator\PortGenerator;
-use Testcontainers\Utils\PortGenerator\RandomUniquePortGenerator;
 use Testcontainers\Utils\PortNormalizer;
 use Testcontainers\Utils\TarBuilder;
 use Testcontainers\Wait\WaitForContainer;
@@ -60,7 +59,7 @@ class GenericContainer implements TestContainer
 
     protected WaitStrategy $waitStrategy;
 
-    protected PortGenerator $portGenerator;
+    protected ?PortGenerator $portGenerator = null;
 
     protected bool $isPrivileged = false;
 
@@ -107,7 +106,6 @@ public function __construct(string $image)
         $this->image = $image;
         $this->dockerClient = DockerContainerClient::getDockerClient();
         $this->waitStrategy = new WaitForContainer();
-        $this->portGenerator = new RandomUniquePortGenerator();
     }
 
     public function getId(): string
@@ -505,7 +503,9 @@ protected function createPortBindings(): array
 
         foreach ($this->exposedPorts as $port) {
             $portBinding = new PortBinding();
-            $portBinding->setHostPort((string)$this->portGenerator->generatePort());
+            if ($this->portGenerator !== null) {
+                $portBinding->setHostPort((string)$this->portGenerator->generatePort());
+            }
             $portBinding->setHostIp('0.0.0.0');
             $portBindings[$port] = [$portBinding];
         }

tests/Unit/Container/GenericContainerTest.php

@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Testcontainers\Tests\Unit\Container;
+
+use Docker\API\Model\ContainersCreatePostBody;
+use Docker\Docker as DockerClient;
+use PHPUnit\Framework\TestCase;
+use RuntimeException;
+use Testcontainers\Container\GenericContainer;
+use Testcontainers\ContainerClient\DockerContainerClient;
+use Testcontainers\Utils\PortGenerator\FixedPortGenerator;
+use Testcontainers\Utils\PortGenerator\PortGenerator;
+
+/**
+ * @covers \Testcontainers\Container\GenericContainer
+ */
+class GenericContainerTest extends TestCase
+{
+    protected function tearDown(): void
+    {
+        (new \ReflectionClass(DockerContainerClient::class))->getProperty('dockerClient')->setValue(null, null);
+        parent::tearDown();
+    }
+
+    /**
+     * @return array<string, array{?PortGenerator, ?string}>
+     */
+    public static function portGenerators(): array
+    {
+        return [
+            'docker allocates by default' => [null, null],
+            'port generator' => [new FixedPortGenerator([8080]), '8080'],
+        ];
+    }
+
+    /**
+     * @dataProvider portGenerators
+     */
+    public function testHostPortOfExposedPort(?PortGenerator $portGenerator, ?string $hostPort): void
+    {
+        $created = null;
+        $docker = $this->createMock(DockerClient::class);
+        $docker->method('containerCreate')->willReturnCallback(
+            static function (ContainersCreatePostBody $body) use (&$created): never {
+                $created = $body;
+                throw new RuntimeException('created');
+            }
+        );
+        DockerContainerClient::setDockerClient($docker);
+        $container = (new GenericContainer('nginx'))->withExposedPorts(80);
+        if ($portGenerator !== null) {
+            $container->withPortGenerator($portGenerator);
+        }
+
+        try {
+            $container->start();
+        } catch (RuntimeException) {
+        }
+
+        self::assertInstanceOf(ContainersCreatePostBody::class, $created);
+        $binding = $created->getHostConfig()?->getPortBindings()['80/tcp'][0] ?? null;
+        self::assertNotNull($binding);
+        self::assertSame($hostPort, $binding->isInitialized('hostPort') ? $binding->getHostPort() : null);
+    }
+}