Ensure $view is an instance of Stringable

Add an assertion to verify that $view implements the Stringable interface before casting it to a string. This enhances type safety and prevents potential runtime errors.

tests/IntegrateTest.php

@@ -12,6 +12,7 @@
 use BEAR\Streamer\Resource\Page\StreamArray;
 use PHPUnit\Framework\TestCase;
 use Ray\Di\Injector;
+use Stringable;
 
 use function assert;
 use function method_exists;
@@ -78,7 +79,8 @@ public function testRender(string $uri, string $expected): void
         $ro->setRenderer($this->renderer);
         assert(method_exists($ro, 'onGet'));
         $view = $ro->onGet();
-        $stream = $this->streamer->getStream((string) $view); // @phpstan-ignore-line
+        assert($view instanceof Stringable);
+        $stream = $this->streamer->getStream((string) $view);
         rewind($stream);
         $view = stream_get_contents($stream);
         $this->assertSame($expected, $view);