Add test for mismatch for y and xarray lenght

Author: bobleesj

src/diffpy/utils/diffraction_objects.py

@@ -346,6 +346,15 @@ def insert_scattering_quantity(
         Nothing.  Updates the object in place.
 
         """
+
+        # Check xarray and yarray have the same length
+        if len(xarray) != len(yarray):
+            raise ValueError(
+                "'xarray' and 'yarray' must have the same length. "
+                "Please re-initialize 'DiffractionObject' or re-run the method 'insert_scattering_quantity' "
+                "with 'xarray' and 'yarray' of identical length."
+            )
+
         self._set_xarrays(xarray, xtype)
         self._all_arrays[:, 0] = yarray
         self._input_xtype = xtype
@@ -360,14 +369,6 @@ def insert_scattering_quantity(
         if wavelength is not None:
             self.wavelength = wavelength
 
-        # Check xarray and yarray have the same length
-        if len(xarray) != len(yarray):
-            raise ValueError(
-                "`xarray` and `yarray` must have the same length. "
-                "Please re-initialize `DiffractionObject` or re-run the method `insert_scattering_quantity` "
-                "with `xarray` and `yarray` of identical length."
-            )
-
         # Check xtype is valid. An empty string is the default value.
         if xtype != "":
             if xtype not in XQUANTITIES:

tests/test_diffraction_objects.py

@@ -411,6 +411,16 @@ def test_all_array_setter():
         actual_do.all_arrays = np.empty((4, 4))
 
 
+def test_xarray_yarray_length_mismatch():
+    with pytest.raises(
+        ValueError,
+        match="'xarray' and 'yarray' must have the same length. "
+        "Please re-initialize 'DiffractionObject' or re-run the method 'insert_scattering_quantity' "
+        "with 'xarray' and 'yarray' of identical length",
+    ):
+        DiffractionObject(xarray=np.array([1.0, 2.0]), yarray=np.array([0.0, 0.0, 0.0]))
+
+
 def test_input_xtype_getter():
     do = DiffractionObject(xtype="tth")
     assert do.input_xtype == "tth"