Function test_eval_dask_assignment

xarray/tests/test_eval.py:436–453

Test that assignments with dask arrays preserve lazy evaluation.

()

@requires_dask
def test_eval_dask_assignment() -> None:
    """Test that assignments with dask arrays preserve lazy evaluation."""
    from xarray.core.utils import is_duck_dask_array

    ds = Dataset(
        {"a": ("x", np.arange(10.0)), "b": ("x", np.linspace(0, 1, 10))}
    ).chunk({"x": 5})

    with raise_if_dask_computes():
        result = ds.eval("z = a + b")

    assert isinstance(result, Dataset)
    assert "z" in result.data_vars
    assert is_duck_dask_array(result["z"].data)

    # Verify correctness when computed
    expected = ds["a"] + ds["b"]
    assert_equal(result["z"], expected)


@requires_dask