add download data step to test

Author: ocefpaf

pixi.toml

@@ -49,10 +49,12 @@ setuptools_scm = "*"
 python-build = "*"
 sphinx-autodoc-typehints = "*"
 myst-nb = "*"
+pooch = "*"
 
 [feature.dev.tasks]
 lint = "ruff check tests xarray_subset_grid"
-test = "pytest tests/"
+test = { cmd = ["pytest", "tests/"], depends-on = ["download"] }
+download = "python download_test_data.py"
 test_all = "pytest --online tests/"
 test_cov = "pytest --cov=xarray_subset_grid tests"