From 74deacca5122667b030d5aeaaaff78ee8492e72e Mon Sep 17 00:00:00 2001
From: Tim Treis <tim.treis@helmholtz-munich.de>
Date: Fri, 19 Jun 2026 19:20:57 +0200
Subject: [PATCH 01/10] Add downloadable cells dataset via scverse-misc

Expose spatialdata.datasets.cells() alongside blobs/raccoon. It downloads
the cells example dataset and loads it as a SpatialData object, reusing the
scverse-misc datasets infrastructure (parse_registry + fetch with the
built-in spatialdata loader) rather than reimplementing a downloader.

- ship src/spatialdata/datasets.yaml registry (base_url + cells.zip sha256)
- add scverse-misc[datasets]>=0.0.10 dependency
- bump requires-python and ruff target to 3.12 (scverse-misc requires >=3.12)
- update CI matrix 3.11 -> 3.12
- docs + network-free registry test and a slow download test

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 docs/api/datasets.md            |  1 +
 pyproject.toml                  |  1 +
 src/spatialdata/datasets.py     | 33 ++++++++++++++++++++++++++++++++-
 src/spatialdata/datasets.yaml   | 15 +++++++++++++++
 tests/datasets/test_datasets.py | 30 +++++++++++++++++++++++++++++-
 5 files changed, 78 insertions(+), 2 deletions(-)
 create mode 100644 src/spatialdata/datasets.yaml

diff --git a/docs/api/datasets.md b/docs/api/datasets.md
index 7bf6d5a61..d0c43b56c 100644
--- a/docs/api/datasets.md
+++ b/docs/api/datasets.md
@@ -7,5 +7,6 @@ Convenience small datasets
 
 .. autofunction:: blobs
 .. autofunction:: blobs_annotating_element
+.. autofunction:: cells
 .. autofunction:: raccoon
 ```
diff --git a/pyproject.toml b/pyproject.toml
index 03181eadb..34592a8e5 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,6 +45,7 @@ dependencies = [
     "spatial_image>=1.2.3",
     "scikit-image",
     "scipy!=1.17.0",
+    "scverse-misc[datasets]>=0.0.10",
     "typing_extensions>=4.8.0",
     "universal_pathlib>=0.2.6",
     "xarray>=2024.10.0",
diff --git a/src/spatialdata/datasets.py b/src/spatialdata/datasets.py
index 37f529c72..be27bf988 100644
--- a/src/spatialdata/datasets.py
+++ b/src/spatialdata/datasets.py
@@ -31,7 +31,7 @@
 )
 from spatialdata.transformations import Identity
 
-__all__ = ["blobs", "raccoon"]
+__all__ = ["blobs", "cells", "raccoon"]
 
 
 def blobs(
@@ -79,6 +79,37 @@ def raccoon() -> SpatialData:
     return RaccoonDataset().raccoon()
 
 
+def cells(path: str | None = None) -> SpatialData:
+    """
+    Cells dataset.
+
+    Download the ``cells`` example dataset and load it as a :class:`~spatialdata.SpatialData`
+    object. The download is hash-verified and cached, so repeated calls reuse the local copy
+    instead of downloading again.
+
+    Parameters
+    ----------
+    path
+        Directory in which to cache the downloaded data. If `None`, the default OS cache
+        location is used (:func:`pooch.os_cache` for ``"spatialdata"``).
+
+    Returns
+    -------
+    SpatialData object with the cells dataset.
+    """
+    import importlib.resources
+    from pathlib import Path
+
+    import pooch
+    from scverse_misc.datasets import fetch, parse_registry
+
+    cache_dir = Path(path) if path is not None else Path(pooch.os_cache("spatialdata"))
+    registry = importlib.resources.files("spatialdata").joinpath("datasets.yaml")
+    with importlib.resources.as_file(registry) as registry_path:
+        base_url, datasets = parse_registry(registry_path)
+    return fetch(datasets["cells"], cache_dir, base_url=base_url)
+
+
 class RaccoonDataset:
     """Raccoon dataset."""
 
diff --git a/src/spatialdata/datasets.yaml b/src/spatialdata/datasets.yaml
new file mode 100644
index 000000000..1811f090c
--- /dev/null
+++ b/src/spatialdata/datasets.yaml
@@ -0,0 +1,15 @@
+# Registry of downloadable example datasets for ``spatialdata.datasets``.
+#
+# Parsed by ``scverse_misc.datasets.parse_registry`` and fetched (downloaded,
+# hash-verified, cached and loaded) via ``scverse_misc.datasets.fetch``.
+#
+#   type: spatialdata  ->  a .zip that extracts to a single .zarr store
+base_url: https://exampledata.scverse.org/spatialdata/
+datasets:
+  cells:
+    type: spatialdata
+    doc_header: Cells dataset as a SpatialData object.
+    files:
+      - name: cells.zip
+        s3_key: cells.zip
+        sha256: dc9613cb9e16fd2cd8d83f3a9586eeda4af5ba8ba366f1066efb51305820c5fb
diff --git a/tests/datasets/test_datasets.py b/tests/datasets/test_datasets.py
index 2237e253c..10337915f 100644
--- a/tests/datasets/test_datasets.py
+++ b/tests/datasets/test_datasets.py
@@ -1,6 +1,11 @@
 from __future__ import annotations
 
-from spatialdata.datasets import blobs, raccoon
+import importlib.resources
+
+import pytest
+
+from spatialdata import SpatialData
+from spatialdata.datasets import blobs, cells, raccoon
 
 
 def test_datasets() -> None:
@@ -26,3 +31,26 @@ def test_datasets() -> None:
     assert sdata_raccoon.images["raccoon"].shape == (3, 768, 1024)
     assert sdata_raccoon.labels["segmentation"].shape == (768, 1024)
     _ = str(sdata_raccoon)
+
+
+def test_cells_registry() -> None:
+    # Network-free: the shipped registry parses and exposes the cells dataset.
+    from scverse_misc.datasets import parse_registry
+
+    registry = importlib.resources.files("spatialdata").joinpath("datasets.yaml")
+    with importlib.resources.as_file(registry) as registry_path:
+        base_url, datasets = parse_registry(registry_path)
+
+    assert base_url == "https://exampledata.scverse.org/spatialdata/"
+    entry = datasets["cells"]
+    assert entry.type == "spatialdata"
+    file = entry.file(name="cells.zip")
+    assert file.sha256 == "dc9613cb9e16fd2cd8d83f3a9586eeda4af5ba8ba366f1066efb51305820c5fb"
+    assert file.resolve_url(base_url) == "https://exampledata.scverse.org/spatialdata/cells.zip"
+
+
+@pytest.mark.slow
+def test_cells_download(tmp_path) -> None:
+    # Downloads ~3 MB from the scverse example data bucket; opt out with `-m "not slow"`.
+    sdata = cells(path=str(tmp_path))
+    assert isinstance(sdata, SpatialData)

From c453909ef793bc8c750d20acd8a4138b30669e1d Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 19 Jun 2026 17:22:38 +0000
Subject: [PATCH 02/10] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 src/spatialdata/datasets.yaml | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/spatialdata/datasets.yaml b/src/spatialdata/datasets.yaml
index 1811f090c..9f5d235a1 100644
--- a/src/spatialdata/datasets.yaml
+++ b/src/spatialdata/datasets.yaml
@@ -6,10 +6,10 @@
 #   type: spatialdata  ->  a .zip that extracts to a single .zarr store
 base_url: https://exampledata.scverse.org/spatialdata/
 datasets:
-  cells:
-    type: spatialdata
-    doc_header: Cells dataset as a SpatialData object.
-    files:
-      - name: cells.zip
-        s3_key: cells.zip
-        sha256: dc9613cb9e16fd2cd8d83f3a9586eeda4af5ba8ba366f1066efb51305820c5fb
+    cells:
+        type: spatialdata
+        doc_header: Cells dataset as a SpatialData object.
+        files:
+            - name: cells.zip
+              s3_key: cells.zip
+              sha256: dc9613cb9e16fd2cd8d83f3a9586eeda4af5ba8ba366f1066efb51305820c5fb

From 49d0309a6bb71847621ca179d6056df40efe6fb8 Mon Sep 17 00:00:00 2001
From: anon <tim.treis@helmholtz-munich.de>
Date: Mon, 22 Jun 2026 12:17:35 +0200
Subject: [PATCH 03/10] Fix mypy no-any-return in cells()

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 src/spatialdata/datasets.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/spatialdata/datasets.py b/src/spatialdata/datasets.py
index be27bf988..8b0233f68 100644
--- a/src/spatialdata/datasets.py
+++ b/src/spatialdata/datasets.py
@@ -107,7 +107,8 @@ def cells(path: str | None = None) -> SpatialData:
     registry = importlib.resources.files("spatialdata").joinpath("datasets.yaml")
     with importlib.resources.as_file(registry) as registry_path:
         base_url, datasets = parse_registry(registry_path)
-    return fetch(datasets["cells"], cache_dir, base_url=base_url)
+    sdata: SpatialData = fetch(datasets["cells"], cache_dir, base_url=base_url)
+    return sdata
 
 
 class RaccoonDataset:

From a48e66de58d5222d4f03b1777f33744bb21b6090 Mon Sep 17 00:00:00 2001
From: anon <tim.treis@helmholtz-munich.de>
Date: Mon, 22 Jun 2026 12:20:49 +0200
Subject: [PATCH 04/10] Bump scverse-misc pin to >=0.1.0 (first released
 datasets version)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index 34592a8e5..3fe577a50 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -45,7 +45,7 @@ dependencies = [
     "spatial_image>=1.2.3",
     "scikit-image",
     "scipy!=1.17.0",
-    "scverse-misc[datasets]>=0.0.10",
+    "scverse-misc[datasets]>=0.1.0",
     "typing_extensions>=4.8.0",
     "universal_pathlib>=0.2.6",
     "xarray>=2024.10.0",

From 5944eda4a8830afb5f5415685cac1c9cc2934dd5 Mon Sep 17 00:00:00 2001
From: anon <tim.treis@helmholtz-munich.de>
Date: Mon, 6 Jul 2026 15:12:18 +0200
Subject: [PATCH 05/10] Add license and attribution to cells dataset registry

The cells dataset is derived from the 10x Genomics Xenium Prime Cervical
Cancer FFPE sample, released under CC BY 4.0 (attribution required). Record
the license and attribution in the registry and document the expectation
that every dataset lists its license.
---
 src/spatialdata/datasets.yaml | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/spatialdata/datasets.yaml b/src/spatialdata/datasets.yaml
index 9f5d235a1..9fb07af3b 100644
--- a/src/spatialdata/datasets.yaml
+++ b/src/spatialdata/datasets.yaml
@@ -4,11 +4,19 @@
 # hash-verified, cached and loaded) via ``scverse_misc.datasets.fetch``.
 #
 #   type: spatialdata  ->  a .zip that extracts to a single .zarr store
+#
+# Every dataset must list its ``license``; datasets under a license that requires
+# attribution must also carry an ``attribution`` string crediting the original source.
 base_url: https://exampledata.scverse.org/spatialdata/
 datasets:
     cells:
         type: spatialdata
         doc_header: Cells dataset as a SpatialData object.
+        license: CC BY 4.0
+        attribution: >-
+            Derived from the 10x Genomics Xenium Prime Cervical Cancer FFPE dataset
+            (https://www.10xgenomics.com/datasets/xenium-prime-ffpe-human-cervical-cancer),
+            subset to a small tissue region. Licensed under CC BY 4.0.
         files:
             - name: cells.zip
               s3_key: cells.zip

From d62ede0bae7c2c30966b64a51af06747cfa54cf9 Mon Sep 17 00:00:00 2001
From: anon <tim.treis@helmholtz-munich.de>
Date: Fri, 14 Aug 2026 19:12:28 +0200
Subject: [PATCH 06/10] refactor(datasets): address review on cells()

Extract _shipped_registry() and _cache_dir() helpers, shared between
cells() and the tests, removing the duplicated registry-parsing block.
_cache_dir() isolates the path-vs-default branch so both sides are
covered without a network call.

Describe the dataset contents in the docstring, and assert the concrete
element counts and shapes in test_cells_download.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 src/spatialdata/datasets.py     | 38 ++++++++++++++++++++++++---------
 tests/datasets/test_datasets.py | 30 ++++++++++++++++++++------
 2 files changed, 51 insertions(+), 17 deletions(-)

diff --git a/src/spatialdata/datasets.py b/src/spatialdata/datasets.py
index 8b0233f68..532394d00 100644
--- a/src/spatialdata/datasets.py
+++ b/src/spatialdata/datasets.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import warnings
+from pathlib import Path
 from typing import Any, Literal
 
 import dask.dataframe.core
@@ -79,6 +80,24 @@ def raccoon() -> SpatialData:
     return RaccoonDataset().raccoon()
 
 
+def _shipped_registry() -> tuple[str | None, dict[str, Any]]:
+    """Parse the ``datasets.yaml`` registry shipped inside the ``spatialdata`` package."""
+    import importlib.resources
+
+    from scverse_misc.datasets import parse_registry
+
+    registry = importlib.resources.files("spatialdata").joinpath("datasets.yaml")
+    with importlib.resources.as_file(registry) as registry_path:
+        return parse_registry(registry_path)
+
+
+def _cache_dir(path: str | None) -> Path:
+    """Resolve the cache directory, defaulting to the OS cache location for ``"spatialdata"``."""
+    import pooch
+
+    return Path(path) if path is not None else Path(pooch.os_cache("spatialdata"))
+
+
 def cells(path: str | None = None) -> SpatialData:
     """
     Cells dataset.
@@ -87,6 +106,12 @@ def cells(path: str | None = None) -> SpatialData:
     object. The download is hash-verified and cached, so repeated calls reuse the local copy
     instead of downloading again.
 
+    The dataset is a small region of a Xenium Prime Cervical Cancer sample and contains three
+    multiscale images (``he_aligned``, ``he_image``, ``morphology_focus``), three multiscale
+    label layers (``cell_labels``, ``nucleus_labels``, ``tissue_labels``), the ``transcripts``
+    points, the ``cell_boundaries`` and ``nucleus_boundaries`` shapes, and a cell-by-gene
+    ``table`` annotating the 94 cells.
+
     Parameters
     ----------
     path
@@ -97,17 +122,10 @@ def cells(path: str | None = None) -> SpatialData:
     -------
     SpatialData object with the cells dataset.
     """
-    import importlib.resources
-    from pathlib import Path
+    from scverse_misc.datasets import fetch
 
-    import pooch
-    from scverse_misc.datasets import fetch, parse_registry
-
-    cache_dir = Path(path) if path is not None else Path(pooch.os_cache("spatialdata"))
-    registry = importlib.resources.files("spatialdata").joinpath("datasets.yaml")
-    with importlib.resources.as_file(registry) as registry_path:
-        base_url, datasets = parse_registry(registry_path)
-    sdata: SpatialData = fetch(datasets["cells"], cache_dir, base_url=base_url)
+    base_url, datasets = _shipped_registry()
+    sdata: SpatialData = fetch(datasets["cells"], _cache_dir(path), base_url=base_url)
     return sdata
 
 
diff --git a/tests/datasets/test_datasets.py b/tests/datasets/test_datasets.py
index 10337915f..ad8179b4c 100644
--- a/tests/datasets/test_datasets.py
+++ b/tests/datasets/test_datasets.py
@@ -1,11 +1,12 @@
 from __future__ import annotations
 
-import importlib.resources
+from pathlib import Path
 
+import pooch
 import pytest
 
 from spatialdata import SpatialData
-from spatialdata.datasets import blobs, cells, raccoon
+from spatialdata.datasets import _cache_dir, _shipped_registry, blobs, cells, raccoon
 
 
 def test_datasets() -> None:
@@ -35,11 +36,7 @@ def test_datasets() -> None:
 
 def test_cells_registry() -> None:
     # Network-free: the shipped registry parses and exposes the cells dataset.
-    from scverse_misc.datasets import parse_registry
-
-    registry = importlib.resources.files("spatialdata").joinpath("datasets.yaml")
-    with importlib.resources.as_file(registry) as registry_path:
-        base_url, datasets = parse_registry(registry_path)
+    base_url, datasets = _shipped_registry()
 
     assert base_url == "https://exampledata.scverse.org/spatialdata/"
     entry = datasets["cells"]
@@ -49,8 +46,27 @@ def test_cells_registry() -> None:
     assert file.resolve_url(base_url) == "https://exampledata.scverse.org/spatialdata/cells.zip"
 
 
+def test_cache_dir() -> None:
+    # Network-free: both branches of the cache-directory resolution.
+    assert _cache_dir("/tmp/example") == Path("/tmp/example")
+    assert _cache_dir(None) == Path(pooch.os_cache("spatialdata"))
+
+
 @pytest.mark.slow
 def test_cells_download(tmp_path) -> None:
     # Downloads ~3 MB from the scverse example data bucket; opt out with `-m "not slow"`.
     sdata = cells(path=str(tmp_path))
     assert isinstance(sdata, SpatialData)
+
+    assert set(sdata.images) == {"he_aligned", "he_image", "morphology_focus"}
+    assert sdata.images["he_aligned"]["scale0"]["image"].shape == (3, 430, 540)
+    assert sdata.images["he_image"]["scale0"]["image"].shape == (3, 423, 339)
+    assert sdata.images["morphology_focus"]["scale0"]["image"].shape == (4, 430, 540)
+
+    assert set(sdata.labels) == {"cell_labels", "nucleus_labels", "tissue_labels"}
+    assert sdata.labels["cell_labels"]["scale0"]["image"].shape == (430, 540)
+
+    assert len(sdata.shapes["cell_boundaries"]) == 94
+    assert len(sdata.shapes["nucleus_boundaries"]) == 94
+    assert len(sdata.points["transcripts"].compute()) == 19479
+    assert sdata.tables["table"].shape == (94, 5101)

From b226ab915c5ffa7f42d6e0da8f006fe28bd28a54 Mon Sep 17 00:00:00 2001
From: anon <tim.treis@helmholtz-munich.de>
Date: Fri, 14 Aug 2026 19:18:09 +0200
Subject: [PATCH 07/10] fix(datasets): satisfy mypy no-any-return in
 _shipped_registry

parse_registry is untyped in the mypy env, so returning its result
directly tripped no-any-return; assign through annotated locals.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 src/spatialdata/datasets.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/spatialdata/datasets.py b/src/spatialdata/datasets.py
index 532394d00..82a5631f4 100644
--- a/src/spatialdata/datasets.py
+++ b/src/spatialdata/datasets.py
@@ -88,7 +88,10 @@ def _shipped_registry() -> tuple[str | None, dict[str, Any]]:
 
     registry = importlib.resources.files("spatialdata").joinpath("datasets.yaml")
     with importlib.resources.as_file(registry) as registry_path:
-        return parse_registry(registry_path)
+        base_url: str | None
+        datasets: dict[str, Any]
+        base_url, datasets = parse_registry(registry_path)
+    return base_url, datasets
 
 
 def _cache_dir(path: str | None) -> Path:

From 9c4e6d54696048d01d4c8c316d6b01b801863269 Mon Sep 17 00:00:00 2001
From: Luca Marconato <m.lucalmer@gmail.com>
Date: Tue, 18 Aug 2026 13:47:19 +0200
Subject: [PATCH 08/10] chore: improve attribution and license info

---
 src/spatialdata/datasets.py   | 7 +++++++
 src/spatialdata/datasets.yaml | 4 +++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/spatialdata/datasets.py b/src/spatialdata/datasets.py
index 82a5631f4..51d360203 100644
--- a/src/spatialdata/datasets.py
+++ b/src/spatialdata/datasets.py
@@ -115,6 +115,13 @@ def cells(path: str | None = None) -> SpatialData:
     points, the ``cell_boundaries`` and ``nucleus_boundaries`` shapes, and a cell-by-gene
     ``table`` annotating the 94 cells.
 
+    Notes
+    -----
+    Derived from the 10x Genomics Xenium Prime Cervical Cancer FFPE dataset
+    (https://www.10xgenomics.com/datasets/xenium-prime-ffpe-human-cervical-cancer), subset to a
+    small tissue region. Licensed under `CC BY 4.0 <https://creativecommons.org/licenses/by/4.0/>`_;
+    see ``datasets.yaml`` for the attribution string shipped alongside the data.
+
     Parameters
     ----------
     path
diff --git a/src/spatialdata/datasets.yaml b/src/spatialdata/datasets.yaml
index 9fb07af3b..ee17bdd1c 100644
--- a/src/spatialdata/datasets.yaml
+++ b/src/spatialdata/datasets.yaml
@@ -13,10 +13,12 @@ datasets:
         type: spatialdata
         doc_header: Cells dataset as a SpatialData object.
         license: CC BY 4.0
+        license_url: https://creativecommons.org/licenses/by/4.0/
         attribution: >-
             Derived from the 10x Genomics Xenium Prime Cervical Cancer FFPE dataset
             (https://www.10xgenomics.com/datasets/xenium-prime-ffpe-human-cervical-cancer),
-            subset to a small tissue region. Licensed under CC BY 4.0.
+            subset to a small tissue region. Licensed under CC BY 4.0
+            (https://creativecommons.org/licenses/by/4.0/).
         files:
             - name: cells.zip
               s3_key: cells.zip

From 88b90b2cbe0f585706077225ef86d350ce7b70bf Mon Sep 17 00:00:00 2001
From: Luca Marconato <m.lucalmer@gmail.com>
Date: Tue, 18 Aug 2026 14:05:31 +0200
Subject: [PATCH 09/10] test(datasets): gate network test behind opt-in
 `network` marker

Rename the `slow` marker to `network` and flip it from opt-out
(`-m "not slow"`) to opt-in: tests marked `network` are skipped
unless `--run-network` is passed. Enable the flag in CI so
`test_cells_download` runs there, and document the `license_url`
convention for CC-BY-style datasets in datasets.yaml.
---
 .github/workflows/test.yaml     |  2 +-
 pyproject.toml                  |  2 +-
 src/spatialdata/datasets.yaml   |  4 +++-
 tests/conftest.py               | 15 +++++++++++++++
 tests/datasets/test_datasets.py |  4 ++--
 5 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index eff3010d3..bc65f074a 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -59,7 +59,7 @@ jobs:
                   PLATFORM: ${{ matrix.os }}
                   DISPLAY: :42
               run: |
-                  uv run pytest --cov --color=yes --cov-report=xml -n auto --dist worksteal
+                  uv run pytest --run-network --cov --color=yes --cov-report=xml -n auto --dist worksteal
             - name: Upload coverage to Codecov
               uses: codecov/codecov-action@v6
               with:
diff --git a/pyproject.toml b/pyproject.toml
index 3fe577a50..15631b1ed 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -108,7 +108,7 @@ addopts = [
 ]
 # These are all markers coming from xarray, dask or anndata. Added here to silence warnings.
 markers = [
-    "slow: marks tests as slow (deselect with '-m \"not slow\"')",
+    "network: marks tests that require network access; skipped by default, run with '--run-network'",
     "gpu: run test on GPU using CuPY.",
     "array_api: used by anndata.tests.helpers, not us",
     "skip_with_pyarrow_strings: skipwhen pyarrow string conversion is turned on",
diff --git a/src/spatialdata/datasets.yaml b/src/spatialdata/datasets.yaml
index ee17bdd1c..62e151d45 100644
--- a/src/spatialdata/datasets.yaml
+++ b/src/spatialdata/datasets.yaml
@@ -6,7 +6,9 @@
 #   type: spatialdata  ->  a .zip that extracts to a single .zarr store
 #
 # Every dataset must list its ``license``; datasets under a license that requires
-# attribution must also carry an ``attribution`` string crediting the original source.
+# attribution must also carry an ``attribution`` string crediting the original source, and
+# datasets under a license that requires linking the license (e.g. CC BY 4.0) must also carry
+# a ``license_url`` field.
 base_url: https://exampledata.scverse.org/spatialdata/
 datasets:
     cells:
diff --git a/tests/conftest.py b/tests/conftest.py
index 617acb90c..871b4280f 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -45,6 +45,21 @@
 )
 
 
+def pytest_addoption(parser: pytest.Parser) -> None:
+    parser.addoption(
+        "--run-network", action="store_true", default=False, help="run tests marked 'network' (e.g. dataset downloads)"
+    )
+
+
+def pytest_collection_modifyitems(config: pytest.Config, items: list[pytest.Item]) -> None:
+    if config.getoption("--run-network"):
+        return
+    skip_network = pytest.mark.skip(reason="need --run-network option to run")
+    for item in items:
+        if "network" in item.keywords:
+            item.add_marker(skip_network)
+
+
 def _fast_deepcopy_sdata(sd: SpatialData) -> SpatialData:
     """
     Fast deepcopy for SpatialData objects in tests.
diff --git a/tests/datasets/test_datasets.py b/tests/datasets/test_datasets.py
index ad8179b4c..3fc66370c 100644
--- a/tests/datasets/test_datasets.py
+++ b/tests/datasets/test_datasets.py
@@ -52,9 +52,9 @@ def test_cache_dir() -> None:
     assert _cache_dir(None) == Path(pooch.os_cache("spatialdata"))
 
 
-@pytest.mark.slow
+@pytest.mark.network
 def test_cells_download(tmp_path) -> None:
-    # Downloads ~3 MB from the scverse example data bucket; opt out with `-m "not slow"`.
+    # Downloads ~3 MB from the scverse example data bucket; skipped by default, opt in with `--run-network`.
     sdata = cells(path=str(tmp_path))
     assert isinstance(sdata, SpatialData)
 

From 5451a5352a663b89e78e42dac4c18ff2ac2880f8 Mon Sep 17 00:00:00 2001
From: Luca Marconato <m.lucalmer@gmail.com>
Date: Tue, 18 Aug 2026 14:20:46 +0200
Subject: [PATCH 10/10] chore: restore slow pytest marker

---
 pyproject.toml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pyproject.toml b/pyproject.toml
index 2e7188296..a8bce770a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -108,6 +108,7 @@ addopts = [
 ]
 # These are all markers coming from xarray, dask or anndata. Added here to silence warnings.
 markers = [
+    "slow: marks tests as slow (deselect with '-m \"not slow\"')",
     "network: marks tests that require network access; skipped by default, run with '--run-network'",
     "gpu: run test on GPU using CuPY.",
     "array_api: used by anndata.tests.helpers, not us",