test: adding different UCs tests while keeping function empty

Author: Luiskitsu

news/morphsqueeze.rst

@@ -0,0 +1,23 @@
+**Added:**
+
+* Polynomial squeeze of x-axis of morphed data
+
+**Changed:**
+
+* <news item>
+
+**Deprecated:**
+
+* <news item>
+
+**Removed:**
+
+* <news item>
+
+**Fixed:**
+
+* <news item>
+
+**Security:**
+
+* <news item>

src/diffpy/morph/morphs/morphsqueeze.py

@@ -4,12 +4,8 @@
 class MorphSqueeze(Morph):
     """Squeeze the morph function.
 
-    This applies a polynomial to squeeze the morph non-linearly. The resulting
-    squeezed morph is interpolated to the (trimmed) target grid.
-    Only the overlapping region between the squeezed morph and the target
-    grid is used. The target is trimmed (or not) accordingly, and the final
-    outputs (morph and target) are returned on the same grid, defined by this
-    trimmed target range.
+    This applies a polynomial to squeeze the morph non-linearly. The morphed
+    data is returned on the same grid as the unmorphed data.
 
     Configuration Variables
     -----------------------
@@ -28,9 +24,5 @@ class MorphSqueeze(Morph):
 
     def morph(self, x_morph, y_morph, x_target, y_target):
         Morph.morph(self, x_morph, y_morph, x_target, y_target)
-        if self.squeeze is None:
-            self.x_morph_out = self.x_morph_in
-            self.y_morph_out = self.y_morph_in
-            return self.xyallout
 
         return self.xyallout

tests/test_morphsqueeze.py

@@ -0,0 +1,60 @@
+import numpy as np
+import pytest
+from numpy.polynomial import Polynomial
+
+from diffpy.morph.morphs.morphsqueeze import MorphSqueeze
+
+squeeze_coeffs_list = [
+    # The order of coefficients is [a0, a1, a2, ..., an]
+    # Negative cubic squeeze coefficients
+    [-0.2, -0.01, -0.001, -0.001],
+    # Positive cubic squeeze coefficients
+    [0.2, 0.01, 0.001, 0.001],
+    # Positive and negative cubic squeeze coefficients
+    [0.2, -0.01, 0.002, -0.001],
+    # Quadratic squeeze coefficients
+    [-0.2, 0.005, -0.007],
+    # Linear squeeze coefficients
+    [0.1, 0.3],
+    # 4th order squeeze coefficients
+    [0.2, -0.01, 0.001, -0.001, 0.0004],
+    # Zeros and non-zeros, the full polynomial is applied
+    [0, 0.03, 0, -0.001],
+    # Testing zeros, expect no squeezing
+    [0, 0, 0, 0, 0, 0],
+]
+morph_target_grids = [
+    # UCs from issue 181: https://github.com/diffpy/diffpy.morph/issues/181
+    # UC2: Same grid
+    (np.linspace(0, 10, 101), np.linspace(0, 10, 101)),
+    # UC4: Target extends beyond morph
+    (np.linspace(0, 10, 101), np.linspace(-2, 20, 221)),
+    # UC6: Target extends beyond morph; morph coarser
+    (np.linspace(0, 10, 101), np.linspace(-2, 20, 421)),
+    # UC8: Target extends beyond morph; target coarser
+    (np.linspace(0, 10, 401), np.linspace(-2, 20, 200)),
+    # UC10: morph starts earlier than target
+    (np.linspace(-2, 10, 121), np.linspace(0, 20, 201)),
+    # UC12: morph extends beyond target
+    (np.linspace(-2, 20, 221), np.linspace(0, 10, 101)),
+]
+
+
+@pytest.mark.parametrize("x_morph, x_target", morph_target_grids)
+@pytest.mark.parametrize("squeeze_coeffs", squeeze_coeffs_list)
+def test_morphsqueeze(x_morph, x_target, squeeze_coeffs):
+    y_target = np.sin(x_target)
+    squeeze_polynomial = Polynomial(squeeze_coeffs)
+    x_squeezed = x_morph + squeeze_polynomial(x_morph)
+    y_morph = np.sin(x_squeezed)
+    x_morph_expected = x_morph
+    y_morph_expected = np.sin(x_morph)
+    morph = MorphSqueeze()
+    morph.squeeze = squeeze_coeffs
+    x_morph_actual, y_morph_actual, x_target_actual, y_target_actual = morph(
+        x_morph, y_morph, x_target, y_target
+    )
+    assert np.allclose(y_morph_actual, y_morph_expected)
+    assert np.allclose(x_morph_actual, x_morph_expected)
+    assert np.allclose(x_target_actual, x_target)
+    assert np.allclose(y_target_actual, y_target)