FIX: bound LOB growth test helper

Reject boolean, zero, oversized chunk counts and invalid chunk sizes before the internal production test binding can enter its simulation loop.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: gargsaumya

mssql_python/pybind/ddbc_bindings.cpp

@@ -519,7 +519,16 @@ size_t ExtendNativeFetchBuffer(std::vector<char>& buffer, size_t currentSize, si
     return requiredSize;
 }
 
-py::tuple TestLobBufferGrowth(size_t chunkCount, size_t chunkSize) {
+py::tuple TestLobBufferGrowth(py::handle chunkCountArg, py::handle chunkSizeArg) {
+    const size_t chunkCount = static_cast<size_t>(
+        ValidateNativeRowCountArgument(chunkCountArg, "LOB growth chunk count", false));
+    if (!PyLong_Check(chunkSizeArg.ptr()) || PyBool_Check(chunkSizeArg.ptr())) {
+        ThrowStdException("LOB growth chunk size must be a positive integer");
+    }
+    const size_t chunkSize = chunkSizeArg.cast<size_t>();
+    if (chunkSize == 0 || chunkSize > MAX_NATIVE_FETCH_BYTES) {
+        ThrowStdException("LOB growth chunk size must be between 1 and 256 MiB");
+    }
     std::vector<char> buffer;
     size_t dataSize = 0;
     size_t reservedBytes = 0;

tests/test_010_pybind_functions.py

@@ -87,6 +87,21 @@ def test_lob_buffer_growth_is_geometric():
     assert growth_count == 7
 
 
+@pytest.mark.skipif(not DDBC_AVAILABLE, reason="ddbc_bindings not available")
+@pytest.mark.parametrize(
+    ("chunk_count", "chunk_size", "message"),
+    [
+        (1_000_001, 1, "chunk count"),
+        (True, 1, "chunk count"),
+        (1, 0, "chunk size"),
+        (1, True, "chunk size"),
+    ],
+)
+def test_lob_buffer_growth_helper_rejects_unsafe_sizes(chunk_count, chunk_size, message):
+    with pytest.raises((RuntimeError, TypeError), match=message):
+        ddbc._test_lob_buffer_growth(chunk_count, chunk_size)
+
+
 @pytest.mark.skipif(not DDBC_AVAILABLE, reason="ddbc_bindings not available")
 class TestPybindModuleInfo:
     """Test module information and architecture detection."""