feat: Add parametrized benchmarks for Zarr v2 and v3 formats

- Extends existing read/write benchmarks to test both v2 and v3
- Parametrizes on zarr_format, compression, layout, and store type
- Skips v2 + sharding combinations (not supported in v2)
- Reuses existing test structure per maintainer feedback
- Provides performance comparison across Zarr versions

Addresses feedback: 'better to reuse existing tests with parametrization'

Author: Claude Subagent

changes/3757.feature.md

@@ -0,0 +1,6 @@
+Add parametrized benchmark tests for both Zarr v2 and v3 formats
+
+- Extends existing read/write benchmarks to test both v2 and v3
+- Parametrizes on zarr_format, compression, layout, and store type
+- Skips v2 + sharding combinations (not supported in v2)
+- Provides performance comparison between Zarr versions

tests/benchmarks/test_e2e.py

@@ -13,6 +13,7 @@
 
     from zarr.abc.store import Store
     from zarr.core.common import NamedConfig
+
 from operator import getitem, setitem
 from typing import Any, Literal
 
@@ -21,13 +22,13 @@
 from zarr import create_array
 
 CompressorName = Literal["gzip"] | None
+ZarrFormat = Literal[2, 3]
 
 compressors: dict[CompressorName, NamedConfig[Any, Any] | None] = {
     None: None,
     "gzip": {"name": "gzip", "configuration": {"level": 1}},
 }
 
-
 layouts: tuple[Layout, ...] = (
     # No shards, just 1000 chunks
     Layout(shape=(1_000_000,), chunks=(1000,), shards=None),
@@ -38,17 +39,28 @@
 )
 
 
+@pytest.mark.parametrize("zarr_format", [2, 3])
 @pytest.mark.parametrize("compression_name", [None, "gzip"])
 @pytest.mark.parametrize("layout", layouts, ids=str)
 @pytest.mark.parametrize("store", ["memory", "local"], indirect=["store"])
 def test_write_array(
-    store: Store, layout: Layout, compression_name: CompressorName, benchmark: BenchmarkFixture
+    store: Store,
+    layout: Layout,
+    compression_name: CompressorName,
+    zarr_format: ZarrFormat,
+    benchmark: BenchmarkFixture,
 ) -> None:
     """
-    Test the time required to fill an array with a single value
+    Test the time required to fill an array with a single value.
+    Parametrized to benchmark both Zarr v2 and v3 formats.
     """
+    # Skip v2 tests with sharding (not supported in v2)
+    if zarr_format == 2 and layout.shards is not None:
+        pytest.skip("Sharding not supported in Zarr v2")
+
     arr = create_array(
         store,
+        zarr_format=zarr_format,
         dtype="uint8",
         shape=layout.shape,
         chunks=layout.chunks,
@@ -60,17 +72,28 @@ def test_write_array(
     benchmark(setitem, arr, Ellipsis, 1)
 
 
+@pytest.mark.parametrize("zarr_format", [2, 3])
 @pytest.mark.parametrize("compression_name", [None, "gzip"])
 @pytest.mark.parametrize("layout", layouts, ids=str)
 @pytest.mark.parametrize("store", ["memory", "local"], indirect=["store"])
 def test_read_array(
-    store: Store, layout: Layout, compression_name: CompressorName, benchmark: BenchmarkFixture
+    store: Store,
+    layout: Layout,
+    compression_name: CompressorName,
+    zarr_format: ZarrFormat,
+    benchmark: BenchmarkFixture,
 ) -> None:
     """
-    Test the time required to fill an array with a single value
+    Test the time required to read an array.
+    Parametrized to benchmark both Zarr v2 and v3 formats.
     """
+    # Skip v2 tests with sharding (not supported in v2)
+    if zarr_format == 2 and layout.shards is not None:
+        pytest.skip("Sharding not supported in Zarr v2")
+
     arr = create_array(
         store,
+        zarr_format=zarr_format,
         dtype="uint8",
         shape=layout.shape,
         chunks=layout.chunks,