For ImageMagick, collect a small fixture set: JPEG with orientation metadata, transparent PNG, animated GIF, wide-gamut image, and a large file. Run the exact resize or conversion command you plan to automate and compare dimensions, color, transparency, file size, and metadata before and after.
Pin the tool version and security policy for production. Avoid overwriting originals until outputs pass visual and automated checks. The right pipeline produces predictable files on every machine, not merely a successful command exit.
Akousa