Changed test assertion for clearer message

tests/PHPUnit/Integration/ServeStaticFileTest.php

@@ -446,8 +446,8 @@ class ServeStaticFileTest extends \PHPUnit_Framework_TestCase
         clearstatcache();
 
         // check the correct compressed file is created
-        $this->assertTrue(file_exists($this->getCompressedFileLocation() . '.' . PARTIAL_BYTE_START . '.' . PARTIAL_BYTE_END . ".deflate"));
-        $this->assertFalse(file_exists($this->getCompressedFileLocation() . ".gz"));
+        $this->assertFileExists($this->getCompressedFileLocation() . '.' . PARTIAL_BYTE_START . '.' . PARTIAL_BYTE_END . ".deflate");
+        $this->assertFileNotExists($this->getCompressedFileLocation() . ".gz");
 
         // check $partialResponse
         $expectedPartialContents = substr(file_get_contents(TEST_FILE_LOCATION), PARTIAL_BYTE_START,
@@ -475,8 +475,8 @@ class ServeStaticFileTest extends \PHPUnit_Framework_TestCase
         clearstatcache();
 
         // check the correct compressed file is created
-        $this->assertTrue(file_exists($this->getCompressedFileLocation() . ".deflate"));
-        $this->assertFalse(file_exists($this->getCompressedFileLocation() . ".gz"));
+        $this->assertFileExists($this->getCompressedFileLocation() . ".deflate");
+        $this->assertFileNotExists($this->getCompressedFileLocation() . ".gz");
 
         // check $fullResponse
         $this->assertEquals(file_get_contents(TEST_FILE_LOCATION), $fullResponse);