Add initial SQLmem package structure with SQL parser, cache manager, column registry, and tests

tests/test_cache.py

@@ -0,0 +1,61 @@
+import sqlite3
+from pathlib import Path
+
+import pytest
+
+from sqlmem.cache import CacheManager
+
+
+@pytest.fixture
+def cache(tmp_path):
+    c = CacheManager(db_path=tmp_path / "test_cache.db", backup_interval=9999)
+    yield c
+    c.close()
+
+
+@pytest.fixture
+def source_conn():
+    conn = sqlite3.connect(":memory:")
+    conn.execute("CREATE TABLE users (name TEXT, email TEXT, status TEXT)")
+    conn.executemany(
+        "INSERT INTO users VALUES (?, ?, ?)",
+        [("alice", "alice@example.com", "active"), ("bob", "bob@example.com", "inactive")],
+    )
+    conn.commit()
+    yield conn
+    conn.close()
+
+
+def test_table_not_cached_initially(cache):
+    assert cache.is_table_cached("users") is False
+
+
+def test_load_table(cache, source_conn):
+    cache.load_table("users", ["name", "email"], source_conn)
+    assert cache.is_table_cached("users") is True
+
+
+def test_loaded_data_correct(cache, source_conn):
+    cache.load_table("users", ["name", "email"], source_conn)
+    rows = cache.connection.execute("SELECT name, email FROM users").fetchall()
+    assert len(rows) == 2
+    assert ("alice", "alice@example.com") in rows
+
+
+def test_mark_table_refreshed(cache, source_conn):
+    cache.load_table("users", ["name"], source_conn)
+    row = cache.connection.execute(
+        "SELECT row_count FROM _sqlmem_tables WHERE table_name = 'users'"
+    ).fetchone()
+    assert row[0] == 2
+
+
+def test_backup_and_reload(tmp_path, source_conn):
+    db_path = tmp_path / "cache.db"
+    c1 = CacheManager(db_path=db_path, backup_interval=9999)
+    c1.load_table("users", ["name"], source_conn)
+    c1.close()
+
+    c2 = CacheManager(db_path=db_path, backup_interval=9999)
+    assert c2.is_table_cached("users") is True
+    c2.close()