add a read_parquet test

tests/dask_nested/test_io.py

@@ -0,0 +1,31 @@
+import dask_nested as dn
+
+
+def test_read_parquet(test_dataset, tmp_path):
+    """test the reproducibility of read_parquet"""
+
+    # Setup a temporary directory for files
+    nested_save_path = tmp_path / "nested"
+    test_save_path = tmp_path / "test_dataset"
+
+    # Save Nested to Parquet
+    flat_nested = test_dataset.nested.nest.to_flat()
+    flat_nested.to_parquet(nested_save_path, write_index=True)
+
+    # Save Base to Parquet
+    test_dataset[["a", "b"]].to_parquet(test_save_path, write_index=True)
+
+    # Now read
+    base = dn.read_parquet(test_save_path, calculate_divisions=True)
+    nested = dn.read_parquet(nested_save_path, calculate_divisions=True)
+
+    base = base.add_nested(nested, "nested")
+
+    # Check the loaded dataset against the original
+    assert base.divisions == test_dataset.divisions  # equal divisions
+    assert base.compute().equals(test_dataset.compute())  # equal data
+
+    # Check the flat nested datasets
+    base_nested_flat = base.nested.nest.to_flat().compute()
+    test_nested_flat = base.nested.nest.to_flat().compute()
+    assert base_nested_flat.equals(test_nested_flat)