def METHOD_NAME(tmpfile):
    """
    After wrapping, writes to the passed-in stream go to an internal pipe, not
    the stream.
    """
    filename = tmpfile()
    fake_stream = open(filename, "w")
    ws = WrappedStream("fake", fake_stream)
    ws.wrap()
    fake_stream.write("test data\n")
    fake_stream.flush()
    fake_stream.close()
    output = open(filename).read()
    assert output == ""