Doctest failures due to changes in xarray 2025.10

[seisman]

From https://github.com/GenericMappingTools/pygmt/actions/runs/18328409327/job/52198267855, we have two failures in doctests:

=================================== FAILURES ===================================
_____________ [doctest] pygmt.datatypes.image._GMT_IMAGE.to_xarray _____________
109         --------
110         >>> from pygmt.clib import Session
111         >>> with Session() as lib:
112         ...     with lib.virtualfile_out(kind="image") as voutimg:
113         ...         lib.call_module("read", ["@earth_day_01d", voutimg, "-Ti"])
114         ...         # Read the image from the virtual file
115         ...         image = lib.read_virtualfile(voutimg, kind="image")
116         ...         # Convert to xarray.DataArray and use it later
117         ...         da = image.contents.to_xarray()
118         >>> da  # doctest: +NORMALIZE_WHITESPACE, +ELLIPSIS
Differences (unified diff with -expected +actual):
    @@ -1,3 +1,3 @@
    -<xarray.DataArray 'z' (band: 3, y: 180, x: 360)>...
    +<xarray.DataArray 'z' (band: 3, y: 180, x: 360)> Size: 194kB
     array([[[ 10,  10,  10, ...,  10,  10,  10],
             [ 10,  10,  10, ...,  10,  10,  10],
    @@ -24,7 +24,7 @@
             [189, 191, 191, ..., 191, 191, 189]]], dtype=uint8)
     Coordinates:
    -  * y        (y) float64... 89.5 88.5 87.5 86.5 ... -86.5 -87.5 -88.5 -89.5
    -  * x        (x) float64... -179.5 -178.5 -177.5 -176.5 ... 177.5 178.5 179.5
    -  * band     (band) uint8... 1 2 3
    +  * band     (band) uint8 3B 1 2 3
    +  * y        (y) float64 1kB 89.5 88.5 87.5 86.5 ... -86.5 -87.5 -88.5 -89.5
    +  * x        (x) float64 3kB -179.5 -178.5 -177.5 -176.5 ... 177.5 178.5 179.5
     Attributes:
    -    long_name:     z
    +    long_name:  z

/home/runner/work/pygmt/pygmt/pygmt/datatypes/image.py:118: DocTestFailure
_____________ [doctest] pygmt.xarray.backend.GMTBackendEntrypoint ______________
057         description:   Reduced by Gaussian Cartesian filtering (111.2 km fullwidt...
058         actual_range:  [190. 981.]
059         long_name:     elevation (m)
060 
061     Read a multi-band GeoTIFF file using ``raster_kind="image"``
062 
063     >>> da_image = xr.open_dataarray(
064     ...     "@earth_night_01d", engine="gmt", raster_kind="image"
065     ... )
066     >>> da_image  # doctest: +NORMALIZE_WHITESPACE, +ELLIPSIS
Differences (unified diff with -expected +actual):
    @@ -1,8 +1,8 @@
    -<xarray.DataArray 'z' (band: 3, y: 180, x: 360)>...
    +<xarray.DataArray 'z' (band: 3, y: 180, x: 360)> Size: 194kB
     [194400 values with dtype=uint8]
     Coordinates:
    -  * y        (y) float64... 89.5 88.5 87.5 86.5 ... -86.5 -87.5 -88.5 -89.5
    -  * x        (x) float64... -179.5 -178.5 -177.5 -176.5 ... 177.5 178.5 179.5
    -  * band     (band) uint8... 1 2 3
    -Attributes:...
    +  * band     (band) uint8 3B 1 2 3
    +  * y        (y) float64 1kB 89.5 88.5 87.5 86.5 ... -86.5 -87.5 -88.5 -89.5
    +  * x        (x) float64 3kB -179.5 -178.5 -177.5 -176.5 ... 177.5 178.5 179.5
    +Attributes:
         long_name:  z

These failures are caused by changes in pydata/xarray#10778.

[weiji14]

Problem would be how to have the tests pass on both xarray>=2025.10.0 and xarray<2025.10.0, similar situation to #3062 but now we can't just use # doctest: +ELLIPSIS since the line order has changed. It seems like there's a way to skip doctests based on a condition (https://www.sphinx-doc.org/en/master/usage/extensions/doctest.html#skipping-tests-conditionally), need to figure out how that could be applied here possibly.

Edit: Found a way to add a conditional to __doctest_skip__ (https://github.com/scientific-python/pytest-doctestplus/tree/v1.4.0?tab=readme-ov-file#skipping-tests), see #4145.