Fix and improve single grid interpolator tests

geotiepoints/tests/test_geointerpolator.py

@@ -261,7 +261,7 @@ def test_geogrid_interpolation_preserves_dtype(self):
 
     def test_chunked_geogrid_interpolation(self):
         """Test that the interpolator works with both explicit tie-point arrays and swath definition objects."""
-        import dask
+        dask = pytest.importorskip("dask")
 
         x_points = np.array([0, 1, 3, 7])
         y_points = np.array([0, 1, 3, 7, 15])

geotiepoints/tests/test_interpolator.py

@@ -140,7 +140,8 @@ def grid_interpolator():
                      [2, 2, 2, 1],
                      [0, 3, 3, 3],
                      [1, 2, 1, 2],
-                     [4, 4, 4, 4]])
+                     [4, 4, 4, 4]],
+                    dtype=np.float64)
 
     return SingleGridInterpolator((ypoints, xpoints), data)
 
@@ -378,3 +379,21 @@ def test_interpolate_dask(self, grid_interpolator, chunks, expected_chunks):
 
             np.testing.assert_allclose(res, self.expected, atol=2e-9)
             assert interpolate.called
+
+    def test_interpolate_preserves_dtype(self):
+        """Test that interpolation is preserving the dtype."""
+        xpoints = np.array([0, 3, 7, 15])
+        ypoints = np.array([0, 3, 7, 15, 31])
+        data = np.array([[0, 1, 0, 1],
+                        [2, 2, 2, 1],
+                        [0, 3, 3, 3],
+                        [1, 2, 1, 2],
+                        [4, 4, 4, 4]],
+                        dtype=np.float32)
+
+        grid_interpolator = SingleGridInterpolator((ypoints, xpoints), data)
+        fine_x = np.arange(16)
+        fine_y = np.arange(32)
+
+        res = grid_interpolator.interpolate((fine_y, fine_x), method="cubic")
+        assert res.dtype == data.dtype