def METHOD_NAME(self):
    data = b"foobar" * 1500
    chunker = ChunkerFixed(4096, 123)
    fmap = [(0, 123, True), (123, 4096, True), (123 + 4096, 4096, True), (123 + 8192, 4096, True)]
    parts = cf(chunker.chunkify(BytesIO(data), fmap=fmap))
    self.assert_equal(
        parts, [data[0:123], data[123 : 123 + 4096], data[123 + 4096 : 123 + 8192], data[123 + 8192 :]]
    )