The instructor said: "I'll correct your tests tomorrow"
=> The instructor said that she would correct my tests the following day/the next day.
Đây là câu trực tiếp-gián tiếp ở tương lai đơn.
S+said that+S+would+V+the following day/the next day.
Chú ý: đổi "will"thành "would"
đổi"tomorrow"thành the following day/the next day.