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

tests/test_parser.py

@@ -0,0 +1,43 @@
+import pytest
+
+from sqlmem.exceptions import ReadOnlyError, UnsupportedQueryError
+from sqlmem.parser import parse
+
+
+def test_simple_select():
+    result = parse("SELECT name, email FROM users WHERE status = 'active'")
+    assert result.table == "users"
+    # WHERE columns are also extracted — needed for in-memory SQLite filtering
+    assert {"name", "email"}.issubset(set(result.columns))
+    assert "status" in result.columns
+
+
+def test_multiple_columns():
+    result = parse("SELECT a, b, c FROM orders")
+    assert result.table == "orders"
+    assert set(result.columns) == {"a", "b", "c"}
+
+
+def test_insert_raises_readonly():
+    with pytest.raises(ReadOnlyError):
+        parse("INSERT INTO users (name) VALUES ('alice')")
+
+
+def test_update_raises_readonly():
+    with pytest.raises(ReadOnlyError):
+        parse("UPDATE users SET name = 'bob' WHERE id = 1")
+
+
+def test_delete_raises_readonly():
+    with pytest.raises(ReadOnlyError):
+        parse("DELETE FROM users WHERE id = 1")
+
+
+def test_wildcard_raises_unsupported():
+    with pytest.raises(UnsupportedQueryError):
+        parse("SELECT * FROM users")
+
+
+def test_join_raises_unsupported():
+    with pytest.raises(UnsupportedQueryError):
+        parse("SELECT a.name, b.title FROM users a JOIN orders b ON a.id = b.user_id")