test function for get_angle_index

src/diffpy/utils/diffraction_objects.py

@@ -248,15 +248,27 @@ def _set_array_from_range(self, begin, end, step_size=None, n_steps=None):
             array = np.linspace(begin, end, n_steps)
         return array
 
-    def get_angle_index(self, angle):
-        count = 0
-        for i, target in enumerate(self.angles):
-            if angle == target:
+    def get_array_index(self, xtype, value):
+        """
+        returns the index of a given value in the array associated with the specified xtype
+
+        Parameters
+        ----------
+        xtype str
+            the xtype used to access the array
+        value float
+            the target value to search for
+
+        Returns
+        -------
+        the index of the value in the array
+        """
+        if self.on_xtype(xtype) is None:
+            raise ValueError(_xtype_wmsg(xtype))
+        for i, target in enumerate(self.on_xtype(xtype)[0]):
+            if value == target:
                 return i
-            else:
-                count += 1
-        if count >= len(self.angles):
-            raise IndexError(f"WARNING: no angle {angle} found in angles list")
+        raise IndexError(f"WARNING: no matching value {value} found in the {xtype} array.")
 
     def _set_xarrays(self, xarray, xtype):
         self.all_arrays = np.empty(shape=(len(xarray), 4))

tests/test_diffraction_objects.py

@@ -1,10 +1,11 @@
+import re
 from pathlib import Path
 
 import numpy as np
 import pytest
 from freezegun import freeze_time
 
-from diffpy.utils.diffraction_objects import DiffractionObject
+from diffpy.utils.diffraction_objects import XQUANTITIES, DiffractionObject
 from diffpy.utils.transforms import wavelength_warning_emsg
 
 
@@ -211,6 +212,44 @@ def _test_valid_diffraction_objects(actual_diffraction_object, function, expecte
     return np.allclose(actual_array, expected_array)
 
 
+def test_get_angle_index():
+    test = DiffractionObject(
+        wavelength=0.71, xarray=np.array([30, 60, 90]), yarray=np.array([1, 2, 3]), xtype="tth"
+    )
+    actual_index = test.get_array_index(xtype="tth", value=30)
+    assert actual_index == 0
+
+
+params_index_bad = [
+    # UC1: empty array
+    (
+        [0.71, np.array([]), np.array([]), "tth", "tth", 10],
+        [IndexError, "WARNING: no matching value 10 found in the tth array."],
+    ),
+    # UC2: invalid xtype
+    (
+        [None, np.array([]), np.array([]), "tth", "invalid", 10],
+        [
+            ValueError,
+            f"WARNING: I don't know how to handle the xtype, 'invalid'.  "
+            f"Please rerun specifying an xtype from {*XQUANTITIES, }",
+        ],
+    ),
+    # UC3: pre-defined array with non-matching value
+    (
+        [0.71, np.array([30, 60, 90]), np.array([1, 2, 3]), "tth", "q", 30],
+        [IndexError, "WARNING: no matching value 30 found in the q array."],
+    ),
+]
+
+
+@pytest.mark.parametrize("inputs, expected", params_index_bad)
+def test_get_angle_index_bad(inputs, expected):
+    test = DiffractionObject(wavelength=inputs[0], xarray=inputs[1], yarray=inputs[2], xtype=inputs[3])
+    with pytest.raises(expected[0], match=re.escape(expected[1])):
+        test.get_array_index(xtype=inputs[4], value=inputs[5])
+
+
 def test_dump(tmp_path, mocker):
     x, y = np.linspace(0, 5, 6), np.linspace(0, 5, 6)
     directory = Path(tmp_path)