Document for YAML TEST case syntax

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Add document explanation/specification for yaml test case. As some of the key may be too complex, e.g `dataProvider`, `expectProvider`

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Look for existing YAML test cases in the repository to understand the current syntax, especially for complex keys like dataProvider and expectProvider. Review the test directory structure and any existing documentation. The goal is to create a clear specification document explaining the YAML test case format.

Written by the indexing model from the issue text.