docstr: Warning should be raised if len(x) <= NFFT.
docstr_tok: ["Warning","should","be","raised","if","len","(","x",")","<","=","NFFT","."]
code: def test_specgram_warn_only1seg(self):
      """Warning should be raised if len(x) <= NFFT."""
      with pytest.warns(
          UserWarning, match="Only one segment is calculated"
      ):
          mlab.specgram(x=self.y, NFFT=len(self.y), Fs=self.Fs)
  
imports: from numpy.testing import assert_allclose, assert_almost_equal, assert_array_equal, assert_array_almost_equal_nulp
  import numpy
  import pytest
  from matplotlib import mlab
label_desc: Use image node_id 18 for calling the TestSpectral obj's underlying member method code with example usage: obj.test_specgram_warn_only1seg() without return types