Add unit tests for fit_ellipse_to_points to address issue #36

README.md

@@ -49,6 +49,15 @@ cd derotation
 pip install .
 ```
 
+## Running Tests
+
+This project uses [pytest](https://docs.pytest.org/) for unit testing. To run the tests, use the following command from the repository root:
+
+```bash
+pytest
+
+
+
 ## Configuration
 Navigate to the `derotation/config/` directory to access and edit the configuration files. You'll find two examples: `full_rotation.yml` for full rotations and `incremental_rotation.yml` for incremental rotations.
 

tests/test_fit_ellipse.py

@@ -0,0 +1,44 @@
+import numpy as np
+import pytest
+from derotation.fit_ellipse import fit_ellipse_to_points  # Adjust this import if needed
+
+def generate_ellipse_points(center, axes, angle, num_points=100):
+    """
+    Generate a set of points along an ellipse.
+
+    Parameters:
+      center (tuple): (cx, cy) center of the ellipse.
+      axes (tuple): (a, b) semi-axes lengths.
+      angle (float): rotation angle in radians.
+      num_points (int): number of points to generate.
+
+    Returns:
+      numpy.ndarray: Array of shape (num_points, 2) with (x, y) coordinates.
+    """
+    t = np.linspace(0, 2 * np.pi, num_points)
+    x = axes[0] * np.cos(t)
+    y = axes[1] * np.sin(t)
+    # Rotate the points by the given angle
+    cos_angle, sin_angle = np.cos(angle), np.sin(angle)
+    x_rot = cos_angle * x - sin_angle * y + center[0]
+    y_rot = sin_angle * x + cos_angle * y + center[1]
+    return np.column_stack((x_rot, y_rot))
+
+def test_fit_ellipse_center():
+    # Define known parameters for the synthetic ellipse
+    known_center = (10.0, 20.0)
+    axes = (5.0, 3.0)
+    angle = np.pi / 6  # 30 degrees in radians
+
+    # Generate points on the ellipse with the known parameters
+    points = generate_ellipse_points(known_center, axes, angle)
+
+    # Fit an ellipse to these points using the function under test
+    fitted_params = fit_ellipse_to_points(points)
+
+    # Check that the returned parameters include a 'center'
+    fitted_center = fitted_params.get('center')
+    assert fitted_center is not None, "The fitted parameters must include a 'center' key."
+
+    # Validate that the fitted center is close to the known center within a tolerance
+    np.testing.assert_allclose(fitted_center, known_center, atol=1e-1)