Better tests and fix .cf.plot() (#11)

* Add proper plotting tests

* xfail coarsen tests.

See xarray GH4120. Coarsen reductions modify attrs on the original object, so
this needs to be last to prevent other tests from failing. This test will also
fail.

* fix .cf.plot(...)

* slightly nicer

Author: dcherian

cf_xarray/accessor.py

@@ -87,9 +87,10 @@ def __init__(self, obj, accessor):
         self._keys = ("x", "y", "hue", "col", "row")
 
     def __call__(self, *args, **kwargs):
-        return _getattr(
+        plot = _getattr(
             obj=self._obj, attr="plot", accessor=self.accessor, keys=self._keys
         )
+        return plot(*args, **kwargs)
 
     def __getattr__(self, attr):
         return _getattr(

cf_xarray/tests/test_accessor.py

@@ -21,8 +21,16 @@
     (
         ("resample", {"time": "M"}, {"T": "M"}),
         ("rolling", {"lat": 5}, {"Y": 5}),
-        ("coarsen", {"lon": 2, "lat": 5}, {"X": 2, "Y": 5}),
-        ("groupby", {"group": "time"}, {"group": "T"})
+        ("groupby", {"group": "time"}, {"group": "T"}),
+        pytest.param(
+            "coarsen",
+            {"lon": 2, "lat": 5},
+            {"X": 2, "Y": 5},
+            marks=pytest.mark.skip(
+                reason="xarray GH4120. any test after this will fail since attrs are lost"
+            ),
+        ),
+        # order of above tests is important: See xarray GH4120
         # groupby("time.day")?
         # groupby_bins
         # weighted
@@ -68,19 +76,24 @@ def test_args_methods(obj):
 @pytest.mark.parametrize("obj", dataarrays)
 def test_dataarray_plot(obj):
 
-    obj.isel(time=1).cf.plot(x="X", y="Y")
+    rv = obj.isel(time=1).cf.plot(x="X", y="Y")
+    assert isinstance(rv, mpl.collections.QuadMesh)
     plt.close()
 
-    obj.isel(time=1).cf.plot.contourf(x="X", y="Y")
+    rv = obj.isel(time=1).cf.plot.contourf(x="X", y="Y")
+    assert isinstance(rv, mpl.contour.QuadContourSet)
     plt.close()
 
-    obj.cf.plot(x="X", y="Y", col="T")
+    rv = obj.cf.plot(x="X", y="Y", col="T")
+    assert isinstance(rv, xr.plot.FacetGrid)
     plt.close()
 
-    obj.cf.plot.contourf(x="X", y="Y", col="T")
+    rv = obj.cf.plot.contourf(x="X", y="Y", col="T")
+    assert isinstance(rv, xr.plot.FacetGrid)
     plt.close()
 
-    obj.isel(lat=[0, 1], lon=1).cf.plot.line(x="T", hue="Y")
+    rv = obj.isel(lat=[0, 1], lon=1).cf.plot.line(x="T", hue="Y")
+    assert all([isinstance(line, mpl.lines.Line2D) for line in rv])
     plt.close()