diff --git a/tests/applications/landlord_description_overrides/__init__.py b/tests/applications/landlord_description_overrides/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/tests/applications/landlord_description_overrides/test_build_columns.py b/tests/applications/landlord_description_overrides/test_build_columns.py
new file mode 100644
index 00000000..aff2f290
--- /dev/null
+++ b/tests/applications/landlord_description_overrides/test_build_columns.py
@@ -0,0 +1,27 @@
+"""The landlord-description-overrides handler's column wiring (`_build_columns`).
+
+A `column_mapping` entry of ``{category -> source header}`` must produce a
+ClassifiableColumn that reads the named header and classifies into the
+category's enum. This pins the main_fuel category onto the wiring.
+"""
+
+from __future__ import annotations
+
+from typing import cast
+
+from applications.landlord_description_overrides.handler import _build_columns
+from infrastructure.chatgpt.chatgpt import ChatGPT
+
+
+def test_build_columns_wires_a_main_fuel_classifier_column() -> None:
+    # Arrange — the factory only stores the injected collaborators, so a bare
+    # object stands in for the (I/O-bound) ChatGPT client and the DB session.
+    chat_gpt = cast(ChatGPT, object())
+
+    # Act
+    columns = _build_columns({"main_fuel": "Main Fuel"}, chat_gpt, None)
+
+    # Assert — one column, named main_fuel, reading the "Main Fuel" header.
+    assert len(columns) == 1
+    assert columns[0].name == "main_fuel"
+    assert columns[0].source_column == "Main Fuel"