def METHOD_NAME(test_results_dir):
    """
    Merge all junitxml generated reports in a single one.
    :param test_results_dir: output dir containing the junitxml reports to merge.
    """
    merged_xml = JUnitXml()
    for dir, _, files in os.walk(test_results_dir):
        for file in files:
            if file.endswith("results.xml"):
                merged_xml += JUnitXml.fromfile(os.path.join(dir, file))
    merged_xml.write("{0}/test_report.xml".format(test_results_dir), pretty=True)