Change test_grdgradient.py to use static_earth_relief (GenericMapping…

…Tools#1679)

pygmt/tests/test_grdgradient.py

@@ -3,54 +3,68 @@
 """
 import os
 
-import numpy.testing as npt
 import pytest
-from pygmt import grdgradient, grdinfo
-from pygmt.datasets import load_earth_relief
+import xarray as xr
+from pygmt import grdgradient, load_dataarray
 from pygmt.exceptions import GMTInvalidInput
 from pygmt.helpers import GMTTempFile
+from pygmt.helpers.testing import load_static_earth_relief
 
 
 @pytest.fixture(scope="module", name="grid")
 def fixture_grid():
     """
-    Load the grid data from the sample earth_relief file.
+    Load the grid data from the static_earth_relief file.
     """
-    return load_earth_relief(resolution="01d", region=[-5, 5, -5, 5])
+    return load_static_earth_relief()
 
 
-def test_grdgradient_outgrid(grid):
+@pytest.fixture(scope="module", name="expected_grid")
+def fixture_grid_result():
+    """
+    Load the expected grdgradient grid result.
+    """
+    return xr.DataArray(
+        data=[
+            [-1.5974800e-03, -9.9056680e-04, -6.1276241e-04, -3.6172546e-04],
+            [-1.5880326e-03, -1.6113354e-03, -5.4624723e-04, -5.0047837e-04],
+            [7.2569086e-04, 2.4801277e-04, 1.8859128e-05, -1.2269041e-03],
+        ],
+        coords=dict(
+            lon=[-52.5, -51.5, -50.5, -49.5],
+            lat=[-19.5, -18.5, -17.5],
+        ),
+        dims=["lat", "lon"],
+    )
+
+
+def test_grdgradient_outgrid(grid, expected_grid):
     """
     Test the azimuth and direction parameters for grdgradient with a set
     outgrid.
     """
     with GMTTempFile(suffix=".nc") as tmpfile:
-        result = grdgradient(grid=grid, outgrid=tmpfile.name, azimuth=10, direction="c")
+        result = grdgradient(
+            grid=grid, outgrid=tmpfile.name, azimuth=10, region=[-53, -49, -20, -17]
+        )
         assert result is None  # return value is None
         assert os.path.exists(path=tmpfile.name)  # check that outgrid exists
-        result = (
-            grdinfo(grid=tmpfile.name, force_scan="a", per_column="n").strip().split()
-        )
-    npt.assert_allclose(float(result[4]), -0.0045060496)  # min
-    npt.assert_allclose(float(result[5]), 0.0575332976)  # max
-    # Check spherically weighted statistics below
-    npt.assert_allclose(float(result[10]), 0.000384754501283)  # median
-    npt.assert_allclose(float(result[12]), 0.00285958005568)  # mean
+        temp_grid = load_dataarray(tmpfile.name)
+        xr.testing.assert_allclose(a=temp_grid, b=expected_grid)
 
 
-def test_grdgradient_no_outgrid(grid):
+def test_grdgradient_no_outgrid(grid, expected_grid):
     """
     Test the azimuth and direction parameters for grdgradient with no set
     outgrid.
     """
-    temp_grid = grdgradient(grid=grid, azimuth=10, direction="c")
-    assert temp_grid.dims == ("lat", "lon")
-    assert temp_grid.gmt.gtype == 1  # Geographic grid
-    assert temp_grid.gmt.registration == 1  # Pixel registration
-    npt.assert_allclose(temp_grid.min(), -0.0045060496)
-    npt.assert_allclose(temp_grid.max(), 0.0575332976)
-    npt.assert_allclose(temp_grid.median(), 0.0004889865522272885)
-    npt.assert_allclose(temp_grid.mean(), 0.0028633063193410635)
+    result = grdgradient(grid=grid, azimuth=10, region=[-53, -49, -20, -17])
+    # check information of the output grid
+    assert isinstance(result, xr.DataArray)
+    assert result.gmt.gtype == 1  # Geographic grid
+    assert result.gmt.registration == 1  # Pixel registration
+    # check information of the output grid
+    xr.testing.assert_allclose(a=result, b=expected_grid)
 
 
 def test_grdgradient_fails(grid):