import re


def is_version_number(version):
    """
    Tests whether the given string is a properly formed
    version number (ex: v1.2.3). The test is made using
    the pattern r"v\d+.\d+.\d+$"

    :param str version: The version string to test.

    :rtype: bool
    """
    match = re.match(r"v\d+.\d+.\d+$", version)

    if match:
        return True
    else:
        return False