Refactor tests to show compatibility

Test files currently have loose and strict parsing tests. We should explore Go's strategy of a loose, strict, and compatibility test.

Start by reviewing the existing loose and strict parsing tests and compare them with Go's loose, strict, and compatibility test strategy. Define the compatibility cases and test organization needed to distinguish all three behaviors; done means the revised suite clearly covers each mode.

由索引模型根据 Issue 内容生成。