From 34460382be7ce343642c87b3b5c4aa5024b4db61 Mon Sep 17 00:00:00 2001
From: Patrick Peglar <patrick.peglar@metoffice.gov.uk>
Date: Sun, 2 Feb 2025 23:43:55 +0000
Subject: [PATCH] Add tests for vectors in Transform.from_points.

---
 tests/bridge/test_from_points.py | 137 +++++++++++++++++++++++++++++++
 1 file changed, 137 insertions(+)

diff --git a/tests/bridge/test_from_points.py b/tests/bridge/test_from_points.py
index 80e9c519..605e2e32 100644
--- a/tests/bridge/test_from_points.py
+++ b/tests/bridge/test_from_points.py
@@ -7,6 +7,7 @@
 
 from __future__ import annotations
 
+import cartopy.crs as ccrs
 import numpy as np
 from pyproj import CRS, Transformer
 import pytest
@@ -76,3 +77,139 @@ def test_scalar():
     np.testing.assert_array_equal(Transform.from_points(0, [90]).points, expected)
     np.testing.assert_array_equal(Transform.from_points([0], 90).points, expected)
     np.testing.assert_array_equal(Transform.from_points([0], [90]).points, expected)
+
+
+class TestFromPointsVectors:
+    """Check calculations on attached vectors.
+
+    Mostly testing against previously-obtained results, but we do have examples proving
+    practically correct behaviours : see src/geovista/examples/vector_data
+    """
+
+    @pytest.fixture(autouse=True)
+    def setup(self):
+        """Set useful test constants."""
+        self.lats = np.array([10.0, 80.0, -70.0, 35.0])
+        self.lons = np.array([5.0, 140.0, -200.0, 73])
+        self.easting = 10.0e6 * np.array([1.0, 8.0, 13.0, 25.0])
+        self.northing = 10.0e6 * np.array([-2.0, 5.0, 17.0, -14.0])
+        self.u = np.array([10.0, 20, 15.0, 24.0])
+        self.v = np.array([20.0, -17, 0.0, 33.0])
+        self.w = np.array([15.0, 25, 4.0, -55.0])
+        self.crs_truelatlon = WGS84
+        self.crs_rotatedlatlon = ccrs.RotatedGeodetic(130.0, 65.0).to_wkt()
+        self.crs_northpolar = ccrs.NorthPolarStereo().to_wkt()
+
+    def test_basic(self):
+        """Check basic operation on true-latlon uvw vectors."""
+        mesh = Transform.from_points(
+            xs=self.lons, ys=self.lats, vectors=(self.u, self.v, self.w)
+        )
+        result = mesh["vectors"].T
+        expected = np.array(
+            [
+                [10.385, -29.006, -6.416, -41.658],
+                [10.947, -1.769, -13.627, -54.169],
+                [22.301, 21.668, -3.759, -4.515],
+            ]
+        )
+        assert np.allclose(result, expected, atol=0.001)
+
+    def test_basic__2d_uv(self):
+        """Check operation with only 2 input component arrays (no W)."""
+        mesh = Transform.from_points(
+            xs=self.lons, ys=self.lats, vectors=(self.u, self.v)
+        )
+        result = mesh["vectors"].T
+        expected = np.array(
+            [
+                [-4.331, -25.681, -5.13, -28.485],
+                [9.659, -4.56, -14.095, -11.084],
+                [19.696, -2.952, 0.0, 27.032],
+            ]
+        )
+        assert np.allclose(result, expected, atol=0.001)
+
+    def test_crs(self):
+        """Check operation with alternate latlon-type CRS."""
+        mesh = Transform.from_points(
+            xs=self.lons,
+            ys=self.lats,
+            vectors=(self.u, self.v),
+            crs=self.crs_rotatedlatlon,
+        )
+        result = mesh["vectors"].T
+        expected = np.array(
+            [
+                [-0.474, -17.651, -13.786, -32.429],
+                [15.592, 13.943, -5.499, 21.403],
+                [16.02, -13.529, -2.168, 12.461],
+            ]
+        )
+        assert np.allclose(result, expected, atol=0.001)
+
+    def test__nonlatlon_crs__fail(self):
+        """Check error when attempted with non-latlon CRS."""
+        msg = "Cannot determine wind directions : Target CRS type is not supported.*"
+        with pytest.raises(ValueError, match=msg):
+            _ = Transform.from_points(
+                xs=self.easting,
+                ys=self.northing,
+                vectors=(self.u, self.v),
+                crs=self.crs_northpolar,
+            )
+
+    def test__nonlatloncrs__truelatlon__vectorscrs(self):
+        """Check ok with non-latlon CRS for points but latlon vectors."""
+        mesh = Transform.from_points(
+            xs=self.easting,
+            ys=self.northing,
+            vectors=(self.u, self.v),
+            crs=self.crs_northpolar,
+            vectors_crs=self.crs_truelatlon,
+        )
+        result = mesh["vectors"].T
+        expected = np.array(
+            [
+                [4.722, -8.267, -9.112, -4.879],
+                [13.541, -24.508, -11.915, 40.408],
+                [17.156, -4.472, 0.0, 2.903],
+            ]
+        )
+        assert np.allclose(result, expected, atol=0.001)
+
+    def test__latlon__vectorscrs(self):
+        """Check operation with different specified CRS for vectors only."""
+        mesh = Transform.from_points(
+            xs=self.lons,
+            ys=self.lats,
+            vectors=(self.u, self.v),
+            vectors_crs=self.crs_rotatedlatlon,
+        )
+        result = mesh["vectors"].T
+        expected = np.array(
+            [
+                [-4.066, 25.821, -8.955, -38.46],
+                [16.031, -2.79, -11.93, 1.87],
+                [15.049, 3.804, 1.578, 13.504],
+            ]
+        )
+        assert np.allclose(result, expected, atol=0.001)
+
+    def test__vectors_array_name(self):
+        """Check operation with alternate vectors array name."""
+        mesh = Transform.from_points(
+            xs=self.lons,
+            ys=self.lats,
+            vectors=(self.u, self.v, self.w),
+            vectors_array_name="squiggle",
+        )
+        result = mesh["squiggle"].T
+        expected = np.array(
+            [
+                [10.385, -29.006, -6.416, -41.658],
+                [10.947, -1.769, -13.627, -54.169],
+                [22.301, 21.668, -3.759, -4.515],
+            ]
+        )
+        assert np.allclose(result, expected, atol=0.001)