def METHOD_NAME(self):
    src_data = numpy.array([-1.0,
                            -1.0 / 2.0,
                            -1.0 / 3.0,
                            -1.0 / 4.0,
                            -1.0 / 5.0])
    trg_data = copy.deepcopy(src_data)
    src = blocks.vector_source_f(src_data, False, len(src_data))
    st = blocks.stretch_ff(-1.0 / 5.0, len(src_data))
    dst = blocks.vector_sink_f(len(src_data))
    self.tb.connect(src, st)
    self.tb.connect(st, dst)
    self.tb.run()
    rsl_data = dst.data()
    sum = 0
    for (u, v) in zip(trg_data, rsl_data):
        w = u - v
        sum += w * w
    sum /= float(len(trg_data))
    assert sum < 1e-6