Tweak Abins-Pychop test; LinAlgError is only encountered on Windows

When testing on Linux, Abins returns NaN rather than raise LinAlgError
when the chopper settings are out of range. Our test should detect
both cases and ensure appropriate behaviour in corresponding
situation. (i.e. raise NoTransmissionError)

tests/integration_tests/test_pychop.py

@@ -74,14 +74,25 @@ def _test_against_abins(abins, rf_2d, setting, matrix):
         abins._polyfits = {}
         expected = abins.calculate_sigma(frequencies * MEV_TO_WAVENUMBER) * WAVENUMBER_TO_MEV
     except LinAlgError:
+        # On Windows we get this error instead of passing NaN
+        # Make sure this library agrees it is a no-transmission situation.
+        with pytest.raises(NoTransmissionError):
+            rf_2d.get_resolution_function('PyChop_fit', chopper_package=setting, e_init=energy, chopper_frequency=chopper_frequency
+)
+            return
+
+    if np.any(np.isnan(expected)):
+        # If chopper/energy settings block transmission, width via AbINS is NaN.
+        # This library should raise NoTransmissionError instead.
         with pytest.raises(NoTransmissionError):
             rf_2d.get_resolution_function('PyChop_fit', chopper_package=setting, e_init=energy, chopper_frequency=chopper_frequency)
-    else:
-        rf = rf_2d.get_resolution_function('PyChop_fit', chopper_package=setting, e_init=energy,
-                                           chopper_frequency=chopper_frequency)
-        actual = rf(frequencies)
+            return
+
+    rf = rf_2d.get_resolution_function('PyChop_fit', chopper_package=setting, e_init=energy,
+                                       chopper_frequency=chopper_frequency)
+    actual = rf(frequencies)
 
-        assert_allclose(actual, expected, rtol=1e-5)
+    assert_allclose(actual, expected, rtol=1e-5)
 
 
 @pytest.fixture(scope='module',