adding richer tests of exception raising

Author: sbillinge

src/diffpy/labpdfproc/tests/test_tools.py

@@ -30,8 +30,8 @@ def test_set_wavelength(inputs, expected):
 ]
 
 
-@pytest.mark.parametrize("inputs", params3)
-def test_set_wavelength_bad(inputs):
+@pytest.mark.parametrize("inputs, msg", params3)
+def test_set_wavelength_bad(inputs, msg):
     actual_args = argparse.Namespace(wavelength=inputs[0], anode_type=inputs[1])
-    with pytest.raises(ValueError):
+    with pytest.raises(ValueError, match=msg[0]):
         actual_args.wavelength = set_wavelength(actual_args)