chore: add sparse index dtype checks to assert_equal (#2362)

Author: LiudengZhang

src/anndata/tests/helpers.py

@@ -688,6 +688,11 @@ def assert_equal_sparse(
     exact: bool = False,
     elem_name: str | None = None,
 ):
+    if exact and sparse.issparse(b) and hasattr(a, "indptr") and hasattr(b, "indptr"):
+        assert a.indptr.dtype == b.indptr.dtype, f"{elem_name}: indptr dtype mismatch"
+        assert a.indices.dtype == b.indices.dtype, (
+            f"{elem_name}: indices dtype mismatch"
+        )
     a = asarray(a)
     assert_equal(b, a, exact=exact, elem_name=elem_name)
 

tests/test_helpers.py

@@ -248,6 +248,21 @@ def test_assert_equal_dask_arrays():
     assert_equal(c, d)
 
 
+@pytest.mark.parametrize("attr", ["indices", "indptr"])
+def test_assert_equal_sparse_index_dtype(attr):
+    """assert_equal(exact=True) should detect indptr/indices dtype mismatches."""
+    a = sparse.csr_matrix(np.eye(3))
+    b = sparse.csr_matrix(np.eye(3))
+    setattr(b, attr, getattr(b, attr).astype(np.int64))
+
+    # Non-exact comparison should pass (values are identical)
+    assert_equal(a, b, exact=False)
+
+    # Exact comparison should catch the dtype mismatch
+    with pytest.raises(AssertionError, match=attr):
+        assert_equal(a, b, exact=True)
+
+
 def test_assert_equal_dask_sparse_arrays():
     import dask.array as da
     from scipy import sparse