diff --git a/tests/Sync/ParcelTest.php b/tests/Sync/ParcelTest.php
index d3ae8ad..a95608e 100644
--- a/tests/Sync/ParcelTest.php
+++ b/tests/Sync/ParcelTest.php
@@ -4,6 +4,9 @@ namespace Icicle\Tests\Concurrent\Sync;
 use Icicle\Concurrent\Sync\Parcel;
 use Icicle\Tests\Concurrent\TestCase;
 
+/**
+ * @requires extension shmop
+ */
 class ParcelTest extends TestCase
 {
     public function testConstructor()
@@ -88,6 +91,7 @@ class ParcelTest extends TestCase
 
     /**
      * @group posix
+     * @requires extension pcntl
      */
     public function testSetInSeparateProcess()
     {
@@ -103,6 +107,7 @@ class ParcelTest extends TestCase
 
     /**
      * @group posix
+     * @requires extension pcntl
      */
     public function testFreeInSeparateProcess()
     {
diff --git a/tests/Sync/PosixSemaphoreTest.php b/tests/Sync/PosixSemaphoreTest.php
index dddabc7..ec700ae 100644
--- a/tests/Sync/PosixSemaphoreTest.php
+++ b/tests/Sync/PosixSemaphoreTest.php
@@ -8,6 +8,8 @@ use Icicle\Tests\Concurrent\TestCase;
 
 /**
  * @group posix
+ * @requires extension shmop
+ * @requires extension sysvsem
  */
 class PosixSemaphoreTest extends TestCase
 {
diff --git a/tests/Sync/ThreadedMutexTest.php b/tests/Sync/ThreadedMutexTest.php
index 542e01b..11982bb 100644
--- a/tests/Sync/ThreadedMutexTest.php
+++ b/tests/Sync/ThreadedMutexTest.php
@@ -8,6 +8,7 @@ use Icicle\Tests\Concurrent\TestCase;
 
 /**
  * @group threading
+ * @requires extension pthreads
  */
 class ThreadedMutexTest extends TestCase
 {
@@ -46,6 +47,6 @@ class ThreadedMutexTest extends TestCase
             });
 
             Loop\run();
-        }, 1.5, 1.65);
+        }, 1.5, 1.7);
     }
 }
diff --git a/tests/Sync/ThreadedSemaphoreTest.php b/tests/Sync/ThreadedSemaphoreTest.php
index d3fae23..5976757 100644
--- a/tests/Sync/ThreadedSemaphoreTest.php
+++ b/tests/Sync/ThreadedSemaphoreTest.php
@@ -8,6 +8,7 @@ use Icicle\Tests\Concurrent\TestCase;
 
 /**
  * @group threading
+ * @requires extension pthreads
  */
 class ThreadedSemaphoreTest extends TestCase
 {
@@ -52,6 +53,6 @@ class ThreadedSemaphoreTest extends TestCase
             });
 
             Loop\run();
-        }, 1.5, 1.65);
+        }, 1.5, 1.7);
     }
 }
diff --git a/tests/Threading/LocalObjectTest.php b/tests/Threading/LocalObjectTest.php
index dd695b9..fb9fb22 100644
--- a/tests/Threading/LocalObjectTest.php
+++ b/tests/Threading/LocalObjectTest.php
@@ -82,14 +82,17 @@ class LocalObjectTest extends TestCase
         $this->assertSame($object, $local->deref());
     }
 
+    /**
+     * @requires extension pthreads
+     */
     public function testPromiseInThread()
     {
         $thread = \Thread::from(function () {
             require __DIR__.'/../../vendor/autoload.php';
-            $promise = new LocalObject(new Promise());
+            $promise = new LocalObject(new Promise(function ($resolve, $reject) {}));
         });
 
-        $thread->start(PTHREADS_INHERIT_INI);
+        $thread->start();
         $thread->join();
     }