Add unit tests for grid export functionality

Co-authored-by: lachlangrose <7371904+lachlangrose@users.noreply.github.com>

Author: Copilot

tests/unit/test_grid_export.py

@@ -0,0 +1,145 @@
+"""Unit tests for grid export functionality."""
+
+import tempfile
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import numpy as np
+import pytest
+
+
+def test_export_grid_ascii_basic():
+    """Test ASCII export of a simple grid with scalar data."""
+    # Create a mock mesh object that simulates a PyVista UniformGrid
+    mock_mesh = MagicMock()
+    mock_mesh.n_cells = 8
+    
+    # Mock cell centers
+    mock_cell_centers = MagicMock()
+    mock_cell_centers.points = np.array([
+        [0.5, 0.5, 0.5],
+        [1.5, 0.5, 0.5],
+        [0.5, 1.5, 0.5],
+        [1.5, 1.5, 0.5],
+        [0.5, 0.5, 1.5],
+        [1.5, 0.5, 1.5],
+        [0.5, 1.5, 1.5],
+        [1.5, 1.5, 1.5],
+    ])
+    mock_mesh.cell_centers.return_value = mock_cell_centers
+    
+    # Mock scalar data
+    mock_mesh.active_scalars_name = "scalar_field"
+    mock_mesh.cell_data = {
+        "scalar_field": np.array([1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0])
+    }
+    
+    # Create a temporary file for export
+    with tempfile.NamedTemporaryFile(mode='w', suffix='.txt', delete=False) as f:
+        temp_path = f.name
+    
+    try:
+        # Import the ObjectListWidget to get the export method
+        # We'll test the export method in isolation
+        from loopstructural.gui.visualisation.object_list_widget import ObjectListWidget
+        
+        # Create a minimal instance (viewer and properties_widget can be None for this test)
+        widget = ObjectListWidget(viewer=MagicMock(), properties_widget=None)
+        
+        # Call the export method
+        widget._export_grid_ascii(mock_mesh, temp_path, "test_grid")
+        
+        # Read the exported file
+        with open(temp_path, 'r') as f:
+            lines = f.readlines()
+        
+        # Verify header
+        assert lines[0].strip() == "# ASCII Grid Export: test_grid"
+        assert lines[1].strip() == "# Format: x y z value"
+        assert lines[2].strip() == "# Number of cells: 8"
+        assert lines[3].strip() == "# Scalar field: scalar_field"
+        assert lines[4].strip() == "#"
+        
+        # Verify data lines
+        data_lines = lines[5:]
+        assert len(data_lines) == 8
+        
+        # Verify first data line
+        first_line = data_lines[0].strip().split()
+        assert len(first_line) == 4
+        assert float(first_line[0]) == pytest.approx(0.5, abs=1e-5)
+        assert float(first_line[1]) == pytest.approx(0.5, abs=1e-5)
+        assert float(first_line[2]) == pytest.approx(0.5, abs=1e-5)
+        assert float(first_line[3]) == pytest.approx(1.0, abs=1e-5)
+        
+    finally:
+        # Clean up
+        Path(temp_path).unlink(missing_ok=True)
+
+
+def test_export_grid_ascii_no_scalars():
+    """Test ASCII export when grid has no scalar data."""
+    # Create a mock mesh without scalar data
+    mock_mesh = MagicMock()
+    mock_mesh.n_cells = 4
+    
+    mock_cell_centers = MagicMock()
+    mock_cell_centers.points = np.array([
+        [0.5, 0.5, 0.5],
+        [1.5, 0.5, 0.5],
+        [0.5, 1.5, 0.5],
+        [1.5, 1.5, 0.5],
+    ])
+    mock_mesh.cell_centers.return_value = mock_cell_centers
+    
+    # No scalar data
+    mock_mesh.active_scalars_name = None
+    mock_mesh.cell_data = {}
+    
+    with tempfile.NamedTemporaryFile(mode='w', suffix='.txt', delete=False) as f:
+        temp_path = f.name
+    
+    try:
+        from loopstructural.gui.visualisation.object_list_widget import ObjectListWidget
+        
+        widget = ObjectListWidget(viewer=MagicMock(), properties_widget=None)
+        widget._export_grid_ascii(mock_mesh, temp_path, "test_grid_no_scalars")
+        
+        with open(temp_path, 'r') as f:
+            lines = f.readlines()
+        
+        # Should still create file with zeros
+        assert "# ASCII Grid Export: test_grid_no_scalars" in lines[0]
+        assert len(lines) >= 9  # Header + 4 data lines
+        
+        # Verify that values are zero
+        data_lines = lines[5:]
+        for line in data_lines:
+            if line.strip():
+                parts = line.strip().split()
+                if len(parts) == 4:
+                    value = float(parts[3])
+                    assert value == pytest.approx(0.0, abs=1e-5)
+        
+    finally:
+        Path(temp_path).unlink(missing_ok=True)
+
+
+def test_mesh_type_detection():
+    """Test that grid mesh types are correctly detected."""
+    test_cases = [
+        ("UniformGrid", True),
+        ("ImageData", True),
+        ("StructuredGrid", True),
+        ("RectilinearGrid", True),
+        ("PolyData", False),
+        ("UnstructuredGrid", False),
+    ]
+    
+    for mesh_type, expected_is_grid in test_cases:
+        mock_mesh = MagicMock()
+        mock_mesh.__class__.__name__ = mesh_type
+        
+        is_grid = type(mock_mesh).__name__ in ['UniformGrid', 'ImageData', 'StructuredGrid', 'RectilinearGrid']
+        
+        assert is_grid == expected_is_grid, f"Failed for mesh type: {mesh_type}"