diff --git a/.travis.yml b/.travis.yml
index 17cf639..1c5e904 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,9 @@ before_script:
   - phpenv config-rm xdebug.ini
   - composer install
 
+before_install:
+  - printf "\n" | pecl install swoole
+
 env:
   - TASK=tests-unit
   - TASK=tests-examples
diff --git a/src/Adapter/Swoole/EventLoop.php b/src/Adapter/Swoole/EventLoop.php
index adbc9b1..0211e4c 100644
--- a/src/Adapter/Swoole/EventLoop.php
+++ b/src/Adapter/Swoole/EventLoop.php
@@ -77,7 +77,6 @@ private function pushCoroutine(): void
         $cid = Coroutine::getCid();
         $this->cids[] = $cid;
         Coroutine::yield();
-
     }
 
     private function createPromise(): DummyPromise
diff --git a/src/Adapter/Swoole/Internal/DummyPromise.php b/src/Adapter/Swoole/Internal/DummyPromise.php
index 5d3be27..c6735ad 100644
--- a/src/Adapter/Swoole/Internal/DummyPromise.php
+++ b/src/Adapter/Swoole/Internal/DummyPromise.php
@@ -8,24 +8,16 @@
 
 final class DummyPromise implements Promise, Deferred
 {
-    /**
-     * @var bool
-     */
+    /** @var bool */
     private $isPending;
 
-    /**
-     * @var mixed
-     */
+    /** @var mixed */
     private $value;
 
-    /**
-     * @var Throwable|null
-     */
+    /** @var Throwable|null */
     private $exception;
 
-    /**
-     * @var callable[]
-     */
+    /** @var callable[] */
     private $callbacks;
 
     public function __construct(?callable $callback = null)
diff --git a/src/Adapter/Swoole/YieldEventLoop.php b/src/Adapter/Swoole/YieldEventLoop.php
index 8b54c34..b40ba49 100644
--- a/src/Adapter/Swoole/YieldEventLoop.php
+++ b/src/Adapter/Swoole/YieldEventLoop.php
@@ -66,11 +66,12 @@ public function async(\Generator $generator): Promise
             Coroutine::create(function () use ($generator, $deferred, $fnWrapGenerator) {
                 if (!$generator->valid()) {
                     $deferred->resolve($generator->getReturn());
+
                     return;
                 }
 
                 $promise = DummyPromise::wrap($generator->current());
-                if($this->isPending($promise)) {
+                if ($this->isPending($promise)) {
                     $cid = Coroutine::getCid();
                     $promise->addCallback(function () use ($cid) {
                         Coroutine::resume($cid);
@@ -96,7 +97,7 @@ public function promiseAll(Promise ...$promises): Promise
         $wg = new Coroutine\WaitGroup();
         $result = [];
         foreach ($promises as $index => $promise) {
-            $this->async((static function() use($wg, &$result, $index, $promise){
+            $this->async((static function () use ($wg, &$result, $index, $promise) {
                 $wg->add();
                 $result[$index] = yield $promise;
                 $wg->done();
@@ -104,7 +105,7 @@ public function promiseAll(Promise ...$promises): Promise
         }
 
         $deferred = $this->deferred();
-        Coroutine::create(function() use($wg, $deferred, &$result) {
+        Coroutine::create(function () use ($wg, $deferred, &$result) {
             $wg->wait();
             $deferred->resolve($result);
         });