From 404213a69cdc11b9703967f5abccaedd8053742c Mon Sep 17 00:00:00 2001
From: Nathan Zimmerman <npzimmerman@gmail.com>
Date: Wed, 19 Feb 2025 09:11:04 -0600
Subject: [PATCH] Clarify intent of roundtrip tests

---
 tests/test_properties.py | 64 ++++++++++++++++++++++++++--------------
 1 file changed, 42 insertions(+), 22 deletions(-)

diff --git a/tests/test_properties.py b/tests/test_properties.py
index d11086beea..f171aaf052 100644
--- a/tests/test_properties.py
+++ b/tests/test_properties.py
@@ -153,15 +153,56 @@ def test_vindex(data: st.DataObject) -> None:
 
 
 @given(store=stores, meta=array_metadata())  # type: ignore[misc]
-async def test_roundtrip_array_metadata(
+async def test_roundtrip_array_metadata_from_store(
     store: Store, meta: ArrayV2Metadata | ArrayV3Metadata
 ) -> None:
+    """
+    Verify that the I/O for metadata in a store are lossless.
+
+    This test serializes an ArrayV2Metadata or ArrayV3Metadata object to a dict
+    of buffers via `to_buffer_dict`, writes each buffer to a store under keys 
+    prefixed with "0/", and then reads them back. The test asserts that each
+    retrieved buffer exactly matches the original buffer.
+    """
     asdict = meta.to_buffer_dict(prototype=default_buffer_prototype())
     for key, expected in asdict.items():
         await store.set(f"0/{key}", expected)
         actual = await store.get(f"0/{key}", prototype=default_buffer_prototype())
         assert actual == expected
 
+@given(data=st.data(), zarr_format=zarr_formats)
+def test_roundtrip_array_metadata_from_json(data: st.DataObject, zarr_format: int) -> None:
+    """
+    Verify that JSON serialization and deserialization of metadata is lossless.
+
+    For Zarr v2:
+      - The metadata is split into two JSON documents (one for array data and one 
+        for attributes). The test merges the attributes back before deserialization.
+    For Zarr v3:
+      - All metadata is stored in a single JSON document. No manual merger is necessary.
+
+    The test then converts both the original and round-tripped metadata objects 
+    into dictionaries using `dataclasses.asdict` and uses a deep equality check 
+    to verify that the roundtrip has preserved all fields (including special 
+    cases like NaN, Infinity, complex numbers, and datetime values).
+    """
+    metadata = data.draw(array_metadata(zarr_formats=st.just(zarr_format)))
+    buffer_dict = metadata.to_buffer_dict(prototype=default_buffer_prototype())
+
+    if zarr_format == 2:
+        zarray_dict = json.loads(buffer_dict[ZARRAY_JSON].to_bytes().decode())
+        zattrs_dict = json.loads(buffer_dict[ZATTRS_JSON].to_bytes().decode())
+        # zattrs and zarray are separate in v2, we have to add attributes back prior to `from_dict`
+        zarray_dict["attributes"] = zattrs_dict
+        metadata_roundtripped = ArrayV2Metadata.from_dict(zarray_dict)
+    else:
+        zarray_dict = json.loads(buffer_dict[ZARR_JSON].to_bytes().decode())
+        metadata_roundtripped = ArrayV3Metadata.from_dict(zarray_dict)
+
+    orig = dataclasses.asdict(metadata)
+    rt = dataclasses.asdict(metadata_roundtripped)
+
+    assert deep_equal(orig, rt), f"Roundtrip mismatch:\nOriginal: {orig}\nRoundtripped: {rt}"
 
 # @st.composite
 # def advanced_indices(draw, *, shape):
@@ -187,27 +228,6 @@ async def test_roundtrip_array_metadata(
 #     assert_array_equal(nparray, zarray[:])
 
 
-@given(data=st.data(), zarr_format=zarr_formats)
-def test_meta_roundtrip(data: st.DataObject, zarr_format: int) -> None:
-    metadata = data.draw(array_metadata(zarr_formats=st.just(zarr_format)))
-    buffer_dict = metadata.to_buffer_dict(prototype=default_buffer_prototype())
-
-    if zarr_format == 2:
-        zarray_dict = json.loads(buffer_dict[ZARRAY_JSON].to_bytes().decode())
-        zattrs_dict = json.loads(buffer_dict[ZATTRS_JSON].to_bytes().decode())
-        # zattrs and zarray are separate in v2, we have to add attributes back prior to `from_dict`
-        zarray_dict["attributes"] = zattrs_dict
-        metadata_roundtripped = ArrayV2Metadata.from_dict(zarray_dict)
-    else:
-        zarray_dict = json.loads(buffer_dict[ZARR_JSON].to_bytes().decode())
-        metadata_roundtripped = ArrayV3Metadata.from_dict(zarray_dict)
-
-    orig = dataclasses.asdict(metadata)
-    rt = dataclasses.asdict(metadata_roundtripped)
-
-    assert deep_equal(orig, rt), f"Roundtrip mismatch:\nOriginal: {orig}\nRoundtripped: {rt}"
-
-
 @given(npst.from_dtype(dtype=np.dtype("float64"), allow_nan=True, allow_infinity=True))
 def test_v2meta_nan_and_infinity(fill_value):
     metadata = ArrayV2Metadata(