Start with two known formulas
The rendering corpus contains mathematical examples. For a minimal file, write inline math as $E=mc^2$ and a display expression on separate lines with $$ delimiters. Some renderers interpret these delimiters; a plain-text viewer shows the source. Both outcomes tell you something about the viewer, not whether the Markdown file is corrupt.
If one expression fails, remove commands until the smallest example remains. Check for an unmatched delimiter, a currency dollar sign interpreted as math, unsupported commands and escaping inside a table or code block. Keep a screenshot of the rendered page and the exact source fragment when reporting a problem.
Know the difference between engines
Aero Markdown’s native project bundles KaTeX for local rendering. Its free browser reader deliberately leaves math as source. Other applications may use KaTeX, MathJax or a narrower parser; the same input need not look identical. Do not claim full LaTeX support without testing the commands you actually use.
The Mac app is not available for public download yet, so this article supplies a reproducible check rather than a published result for a release build. For diagrams rather than formulas, use the Mermaid guide.