Add unittest for cheque fields validation.

test/test_file_validator/test_forms.py

@@ -92,3 +92,11 @@ def test_validate_nc_cc_dep_combination_against_meo_sage_account(
     assert ("Row 1: 'NominalAnalysisNominalCostCentre/1' (Invalid_CC) is not a valid cost centre."
             in str(form.errors["file"][0]))
 
+
+def test_cheque_fields_must_be_empty(sample_input_file: SimpleUploadedFile, mock_meo_database: MagicMock) -> None:
+    """Test that cheque fields must be empty."""
+    modified_file = create_modified_csv(sample_input_file,
+                                        {"ChequeCurrencyName": "USD", "ChequeToBankExchangeRate": "1"})
+    form = CSVUploadForm(files={"file": modified_file})
+    assert not form.is_valid()
+    assert "Row 1: Unexpected values in the Cheque columns. All cheque columns must be empty." in form.errors["file"][0]