📜 WAYPOINT LESSON
Checkpoint: The Integrated Tracker
⭐⭐ intermediate⏳ 15 min read📍 Lesson 120 of 180
Graded checkpoint: the full three-layer expense tracker — validation, upsert, aggregation, and deterministic tie-breaks.
Checkpoint — the integrated system
The full expense tracker, assembled. Failing this checkpoint means one of the milestone contracts broke under integration — the tests will name it.