test: created a test for squeeze morph using sine wave. Created function to test

Author: Luiskitsu

src/diffpy/morph/morphs/morphsqueeze.py

@@ -0,0 +1,52 @@
+"""class MorphSqueeze -- apply a non-linear squeeze to the morph.
+This morph non-linearly adjusts the x-coordinates.
+The y-values are then recomputed by interpolating the original data.
+"""
+
+import numpy as np
+
+from diffpy.morph.morphs.morph import LABEL_GR, LABEL_RA, Morph
+
+
+class MorphSqueeze(Morph):
+    summary = "Squeeze morph by desired amount (non-linear transformation)"
+    xinlabel = LABEL_RA  # This label need to change to be more generic
+    yinlabel = LABEL_GR  # This label need to change to be more generic
+    xoutlabel = LABEL_RA  # This label need to change to be more generic
+    youtlabel = LABEL_GR  # This label need to change to be more generic
+    parnames = ["squeeze"]
+
+    def morph(self, x_morph, y_morph, x_target, y_target):
+        """Resample arrays onto the specified grid using a non-linear squeeze.
+
+        Parameters
+        ----------
+        x_morph : array-like
+            The input x-values to be transformed.
+        y_morph : array-like
+            The input y-values.
+        x_target, y_target : array-like
+            The target grid arrays (left unchanged by this morph).
+
+        Returns
+        -------
+            (x_morph_out, y_morph_out, x_target, y_target)
+        """
+        # Initialize the parent class to set up attributes
+        Morph.morph(self, x_morph, y_morph, x_target, y_target)
+
+        # If squeeze is zero, return original output
+        if self.squeeze == 0:
+            return self.xyallout
+
+        # Compute new x positions using the non-linear squeeze transformation:
+        new_x = self.x_morph_in + self.squeeze * np.sin(self.x_morph_in)
+        self.x_morph_out = new_x
+
+        # Interpolate the y-values at the new x positions.
+        self.y_morph_out = np.interp(new_x, self.x_morph_in, self.y_morph_in)
+
+        return self.xyallout
+
+
+# End of class MorphSqueeze

tests/test_morphsqueeze.py

@@ -0,0 +1,56 @@
+import numpy as np
+import pytest
+
+from diffpy.morph.morphs.morphsqueeze import MorphSqueeze
+
+
+class TestMorphSqueeze:
+    @pytest.fixture
+    def setup(self):
+        # Create a sine-wave for testing
+        self.x_morph = np.linspace(0, 2 * np.pi, 1000)
+        self.y_morph = np.sin(self.x_morph)
+        self.x_target = self.x_morph.copy()
+        self.y_target = self.y_morph.copy()
+        return
+
+    def test_no_squeeze(self, setup):
+        """When squeeze is zero, the input should be unchanged."""
+        morph = MorphSqueeze()
+        morph.squeeze = 0.0
+
+        x_morph, y_morph, x_target, y_target = morph(
+            self.x_morph, self.y_morph, self.x_target, self.y_target
+        )
+
+        # Verify that the morph output matches the original input
+        assert np.allclose(x_morph, self.x_morph)
+        assert np.allclose(y_morph, self.y_morph)
+        # And the target arrays remain unchanged
+        assert np.allclose(x_target, self.x_target)
+        assert np.allclose(y_target, self.y_target)
+
+    def test_morph_with_squeeze(self, setup):
+        """Test that with a non-zero squeeze,
+        x_morph is transformed non-linearly."""
+        morph = MorphSqueeze()
+        morph.squeeze = 0.7
+        x_new, y_new, x_target, y_target = morph(
+            self.x_morph, self.y_morph, self.x_target, self.y_target
+        )
+
+        # Check that target arrays remain unchanged
+        assert np.allclose(self.y_target, y_target)
+
+        # For this test, we expect:
+        # x_new = x_morph + squeeze_factor * sin(x_morph)
+        expected_x = self.x_morph + morph.squeeze * np.sin(self.x_morph)
+        expected_y = np.sin(expected_x)
+
+        # Allow for some tolerance because of numerical interpolation if used
+        res = sum(np.fabs(expected_y - y_new))
+        assert res < 1
+
+
+if __name__ == "__main__":
+    TestMorphSqueeze()