Fix DefaultPool::shutdown()

Forgot to update this to match Worker::shutdown() behavior.

lib/Worker/DefaultPool.php

@@ -35,6 +35,9 @@ final class DefaultPool implements Pool
     /** @var \Closure */
     private $push;
 
+    /** @var \Amp\Promise|null */
+    private $exitStatus;
+
     /**
      * Creates a new worker pool.
      *
@@ -162,8 +165,8 @@ final class DefaultPool implements Pool
      */
     public function shutdown(): Promise
     {
-        if (!$this->isRunning()) {
+        if ($this->exitStatus) {
-            throw new StatusError("The pool was shutdown");
+            return $this->exitStatus;
         }
 
         $this->running = false;
@@ -175,7 +178,7 @@ final class DefaultPool implements Pool
             }
         }
 
-        return Promise\all($shutdowns);
+        return $this->exitStatus = Promise\all($shutdowns);
     }
 
     /**

test/Worker/AbstractPoolTest.php

@@ -42,19 +42,15 @@ abstract class AbstractPoolTest extends TestCase
         });
     }
 
-    /**
+    public function testShutdownShouldReturnSameResult()
-     * @expectedException         \Amp\Parallel\Context\StatusError
-     * @expectedExceptionMessage  The pool was shutdown
-     */
-    public function testShutdownShouldThrowStatusError()
     {
         Loop::run(function () {
             $pool = $this->createPool();
 
             $this->assertTrue($pool->isIdle());
 
-            yield $pool->shutdown();
+            $result = yield $pool->shutdown();
-            yield $pool->shutdown();
+            $this->assertSame($result, yield $pool->shutdown());
         });
     }