add memory optimisation for Backtrace::testFile()

src/Support/Backtrace.php

@@ -25,7 +25,7 @@ final class Backtrace
     {
         $current = null;
 
-        foreach (debug_backtrace() as $trace) {
+        foreach (debug_backtrace(self::BACKTRACE_OPTIONS) as $trace) {
             if (Str::endsWith($trace[self::FILE], (string) realpath('vendor/phpunit/phpunit/src/Util/FileLoader.php'))) {
                 break;
             }