How to Build a Honest Two-Chart Compatibility Engine That Flags Missing Data

A tutorial published on DEV Community outlines a test strategy for building a two-chart compatibility pipeline using BaZi, a traditional symbolic framework, as the domain example. The core engineering goal is to preserve known data, clearly expose unknown data, and ensure every comparison is fully reproducible. The guide emphasizes that missing birth times must never be silently replaced with default values like noon, and that an unknown time should produce no Hour Pillar in the output. It recommends separating chart calculation from comparison logic so that one person's data cannot contaminate the other's, verified through metamorphic tests. Names and display metadata must be kept entirely outside numeric and symbolic calculations, with the system returning observations rather than compatibility verdicts.