enhance tests to check error message

Author: RDaxini

tests/test_modelchain.py

@@ -1785,9 +1785,11 @@ def test_invalid_models(model, sapm_dc_snl_ac_system, location):
         ModelChain(sapm_dc_snl_ac_system, location, **kwargs)
 
 
-def test_bad_get_orientation():
-    with pytest.raises(ValueError):
-        modelchain.get_orientation('bad value')
+def test_get_orientation_invalid_strategy():
+    with pytest.raises(ValueError, 
+                       match='invalid orientation strategy. strategy must '
+                             'be one of south_at_latitude_tilt, flat,'):
+        modelchain.get_orientation('invalid_strategy')
 
 
 # tests for PVSystem with multiple Arrays