✨ feat(sync): add data consistency compare (count + ID-set)

tests/test_sql_writer.py

@@ -10,6 +10,7 @@ credentials are hardcoded here. The test self-cleans using a throwaway
 """
 import os
 import pytest
+from unittest.mock import MagicMock
 
 from sync.sql_writer import SqlWriter, QueueRow
 from sync.config import load_config
@@ -53,3 +54,30 @@ def test_insert_dedup_and_applied_ids():
     finally:
         cur.execute("DELETE dbo.SyncQueue WHERE SourceFile='sqlw_test.accdb'")
         w.close()
+
+
+def _writer_with_cursor(fetchone=None, fetchall=None):
+    """A SqlWriter whose pyodbc connection is a mock (no real connect)."""
+    w = SqlWriter.__new__(SqlWriter)
+    w.conn_str = "dummy"
+    w.queue_table = "dbo.SyncQueue"
+    cur = MagicMock()
+    if fetchone is not None:
+        cur.fetchone.return_value = fetchone
+    if fetchall is not None:
+        cur.fetchall.return_value = fetchall
+    w._conn = MagicMock()
+    w._conn.cursor.return_value = cur
+    return w, cur
+
+
+def test_count_target_executes_count_sql_and_returns_value():
+    w, cur = _writer_with_cursor(fetchone=(7,))
+    assert w.count_target("s", "T_YEAR2026") == 7
+    cur.execute.assert_called_once_with("SELECT COUNT(*) FROM [s].[T_YEAR2026]")
+
+
+def test_read_target_ids_returns_ordered_id_list():
+    w, cur = _writer_with_cursor(fetchall=[(2,), (4,), (6,)])
+    assert w.read_target_ids("s", "T_YEAR2026") == [2, 4, 6]
+    cur.execute.assert_called_once_with("SELECT ID FROM [s].[T_YEAR2026] ORDER BY ID")