diff --git a/tests/StreamTest.php b/tests/StreamTest.php
index bcd3887..f634838 100644
--- a/tests/StreamTest.php
+++ b/tests/StreamTest.php
@@ -38,7 +38,7 @@ abstract class StreamTest extends BaseTest
     public function testWrite()
     {
         if ($this->stream->isWritable()) {
-            $this->assertNull($this->stream->write('foo'));
+            $this->assertIsInt($this->stream->write('foo'));
         } else {
             $this->expectException(RuntimeException::class);
             $this->stream->write('foo');
@@ -105,7 +105,7 @@ abstract class StreamTest extends BaseTest
      */
     public function testEof()
     {
-        $this->assertFalse($this->stream->eof());
+        $this->assertIsBool($this->stream->eof());
     }
 
     /**