Enabled some strict settings

Author: GrahamCampbell

phpunit.xml.dist

@@ -2,14 +2,16 @@
 
 <phpunit backupGlobals="false"
          backupStaticAttributes="false"
+         bootstrap="vendor/autoload.php"
+         beStrictAboutOutputDuringTests="true"
+         beStrictAboutTestsThatDoNotTestAnything="true"
          colors="true"
          convertErrorsToExceptions="true"
          convertNoticesToExceptions="true"
          convertWarningsToExceptions="true"
          processIsolation="false"
          stopOnFailure="true"
          syntaxCheck="true"
-         bootstrap="vendor/autoload.php"
 >
     <testsuites>
         <testsuite name="phpDocumentor\GraphViz">