ref = refs[extension]
    else:
        ref = refs[basename]

    # remove extra content from the top of files
    if extension in ("go", "generatego"):
        data, found = regexs["go_build_constraints"].subn("", data, 1)
    elif extension in ["sh", "py"]:
        data, found = regexs["shebang"].subn("", data, 1)

    data = data.splitlines()

    # if our test file is smaller than the reference it surely fails!