Do not di:compile tests/ folder

Author: kassner

setup/src/Magento/Setup/Console/Command/DiCompileCommand.php

@@ -227,6 +227,7 @@ private function getExcludedModulePaths(array $modulePaths)
 
         $excludedModulePaths = [
             '#^(?:' . join('|', $basePathsRegExps) . ')/Test#',
+            '#^(?:' . join('|', $basePathsRegExps) . ')/tests#',
         ];
         return $excludedModulePaths;
     }
@@ -241,6 +242,7 @@ private function getExcludedLibraryPaths(array $libraryPaths)
     {
         $excludedLibraryPaths = [
             '#^(?:' . join('|', $libraryPaths) . ')/([\\w]+/)?Test#',
+            '#^(?:' . join('|', $libraryPaths) . ')/([\\w]+/)?tests#',
         ];
         return $excludedLibraryPaths;
     }