diff --git a/src/Symfony/Component/Stopwatch/Tests/StopwatchEventTest.php b/src/Symfony/Component/Stopwatch/Tests/StopwatchEventTest.php
index 1ba69d19faff..b0e32c962773 100644
--- a/src/Symfony/Component/Stopwatch/Tests/StopwatchEventTest.php
+++ b/src/Symfony/Component/Stopwatch/Tests/StopwatchEventTest.php
@@ -20,6 +20,8 @@
  */
 class StopwatchEventTest extends \PHPUnit_Framework_TestCase
 {
+    const DELTA = 20;
+
     public function testGetOrigin()
     {
         $event = new StopwatchEvent(12);
@@ -66,20 +68,18 @@ public function testDuration()
     {
         $event = new StopwatchEvent(microtime(true) * 1000);
         $event->start();
-        usleep(20000);
+        usleep(200000);
         $event->stop();
-        $total = $event->getDuration();
-        $this->assertTrue($total >= 11 && $total <= 29, $total.' should be 20 (between 11 and 29)');
+        $this->assertEquals(200, $event->getDuration(), null, self::DELTA);
 
         $event = new StopwatchEvent(microtime(true) * 1000);
         $event->start();
-        usleep(10000);
+        usleep(100000);
         $event->stop();
         $event->start();
-        usleep(10000);
+        usleep(100000);
         $event->stop();
-        $total = $event->getDuration();
-        $this->assertTrue($total >= 11 && $total <= 29, $total.' should be 20 (between 11 and 29)');
+        $this->assertEquals(200, $event->getDuration(), null, self::DELTA);
     }
 
     /**
@@ -96,12 +96,11 @@ public function testEnsureStopped()
         // this also test overlap between two periods
         $event = new StopwatchEvent(microtime(true) * 1000);
         $event->start();
-        usleep(10000);
+        usleep(100000);
         $event->start();
-        usleep(10000);
+        usleep(100000);
         $event->ensureStopped();
-        $total = $event->getDuration();
-        $this->assertTrue($total >= 21 && $total <= 39, $total.' should be 30 (between 21 and 39)');
+        $this->assertEquals(300, $event->getDuration(), null, self::DELTA);
     }
 
     public function testStartTime()
@@ -116,10 +115,9 @@ public function testStartTime()
 
         $event = new StopwatchEvent(microtime(true) * 1000);
         $event->start();
-        usleep(10000);
+        usleep(100000);
         $event->stop();
-        $start = $event->getStartTime();
-        $this->assertTrue($start >= 0 && $start <= 20);
+        $this->assertEquals(0, $event->getStartTime(), null, self::DELTA);
     }
 
     public function testEndTime()
@@ -133,13 +131,12 @@ public function testEndTime()
 
         $event = new StopwatchEvent(microtime(true) * 1000);
         $event->start();
-        usleep(10000);
+        usleep(100000);
         $event->stop();
         $event->start();
-        usleep(10000);
+        usleep(100000);
         $event->stop();
-        $end = $event->getEndTime();
-        $this->assertTrue($end >= 11 && $end <= 29, $end.' should be 20 (between 11 and 29)');
+        $this->assertEquals(200, $event->getEndTime(), null, self::DELTA);
     }
 
     /**
diff --git a/src/Symfony/Component/Stopwatch/Tests/StopwatchTest.php b/src/Symfony/Component/Stopwatch/Tests/StopwatchTest.php
index d1dd2e616bf7..7cb4b64d7915 100644
--- a/src/Symfony/Component/Stopwatch/Tests/StopwatchTest.php
+++ b/src/Symfony/Component/Stopwatch/Tests/StopwatchTest.php
@@ -20,6 +20,8 @@
  */
 class StopwatchTest extends \PHPUnit_Framework_TestCase
 {
+    const DELTA = 20;
+
     public function testStart()
     {
         $stopwatch = new Stopwatch();
@@ -33,26 +35,24 @@ public function testStop()
     {
         $stopwatch = new Stopwatch();
         $stopwatch->start('foo', 'cat');
-        usleep(20000);
+        usleep(200000);
         $event = $stopwatch->stop('foo');
 
         $this->assertInstanceof('Symfony\Component\Stopwatch\StopwatchEvent', $event);
-        $total = $event->getDuration();
-        $this->assertTrue($total > 10 && $total <= 29, $total.' should be 20 (between 10 and 29)');
+        $this->assertEquals(200, $event->getDuration(), null, self::DELTA);
     }
 
     public function testLap()
     {
         $stopwatch = new Stopwatch();
         $stopwatch->start('foo', 'cat');
-        usleep(10000);
+        usleep(100000);
         $event = $stopwatch->lap('foo');
-        usleep(10000);
+        usleep(100000);
         $stopwatch->stop('foo');
 
         $this->assertInstanceof('Symfony\Component\Stopwatch\StopwatchEvent', $event);
-        $total = $event->getDuration();
-        $this->assertTrue($total > 10 && $total <= 29, $total.' should be 20 (between 10 and 29)');
+        $this->assertEquals(200, $event->getDuration(), null, self::DELTA);
     }
 
     /**