Make sure that warning is always triggered.

DietBru · DietBru · commit 379d1287b4a1 · 2017-02-06T20:22:12.000+01:00
diff --git a/lib/matplotlib/tests/test_mlab.py b/lib/matplotlib/tests/test_mlab.py
@@ -2107,6 +2107,7 @@ def test_specgram_phase(self):
     def test_specgram_warn_only1seg(self):
         """Warning should be raised if len(x) <= NFFT. """
         with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always", category=UserWarning)
             mlab.specgram(x=self.y, NFFT=len(self.y), Fs=self.Fs)
         assert len(w) == 1
         assert issubclass(w[0].category, UserWarning)
