diff --git a/src/Container.test.ts b/src/Container.test.ts
new file mode 100644
index 0000000..e7fcc52
--- /dev/null
+++ b/src/Container.test.ts
@@ -0,0 +1,23 @@
+import assert from 'node:assert/strict';
+import { suite, test } from 'node:test';
+import { Container } from './Container.js';
+import { getImageVersionFromDockerfile } from './getImageVersionFromDockerfile.js';
+
+suite('Container', { timeout: 30_000 }, () => {
+	test('starts with a custom port.', async (): Promise<void> => {
+		const imageVersion = getImageVersionFromDockerfile();
+		const container = new Container().withImageTag(imageVersion).withPort(4000);
+
+		await container.start();
+
+		try {
+			const client = container.getClient();
+
+			// Should not throw.
+			await client.ping();
+			assert.ok(container.getMappedPort() > 0);
+		} finally {
+			await container.stop();
+		}
+	});
+});
diff --git a/src/Container.ts b/src/Container.ts
index bb1f093..889915c 100644
--- a/src/Container.ts
+++ b/src/Container.ts
@@ -46,6 +46,8 @@ class Container {
 			'--data-directory-temporary',
 			'--http-enabled',
 			'--https-enabled=false',
+			'--http-port',
+			String(this.#internalPort),
 		];
 
 		const contents: ContentToCopy[] = [];