myProject/.idea/php.xml

<?xml version="1.0" encoding="UTF-8"?>
<project version="4">
  <component name="PhpUnit">
    <phpunit_settings>
      <PhpUnitSettings load_method="CUSTOM_LOADER" custom_loader_path="$PROJECT_DIR$/thinkphp/vendor/autoload.php" />
    </phpunit_settings>
  </component>
</project>