Add test for load() iterable split in UTF-8 char

tests/test_load_iterable.py

@@ -0,0 +1,26 @@
+"""
+Test compatibility with json-stream's support for giving iterables to `load()`.
+"""
+import json_stream
+import pytest
+
+
+@pytest.mark.parametrize("chunk_size", [1, 2, 3, 4, 10])
+def test_chunk_boundary_inside_utf8_char(chunk_size: int) -> None:
+    """
+    Test that chunk boundaries inside UTF-8 chars are handled correctly.
+
+    Regression test for https://github.com/daggaz/json-stream/issues/59.
+    """
+    inner_str = "——"
+    document_str = f'"{inner_str}"'
+    document_bytes = document_str.encode("utf-8")
+
+    iterable = (
+        document_bytes[i : i + chunk_size]
+        for i in range(0, len(document_bytes), chunk_size)
+    )
+
+    parsed = json_stream.load(iterable)
+
+    assert parsed == inner_str