We can try to make the CLI bit more verbose when it is wasm target along with windows error.

Reference:
Originally posted by @lu-zero in xiph/rav1e#2451 (comment)

The Whole UI needs test, but I think most important is to make sure with whatever input is supplied to the command builders fastflix/encoders/<name>/command_builder.py and the general functions in fastflix/encoders/common/helpers.py is the most important to get tests for first.

I have some minimal start on pytests, but would appreciate any help in this effort.

How to reproduce

Please download our sample images.

Then, encode a file with alpha plane:

cavif -i ../avif-sample-images/plum-blossom-small.png -o alpha.avif --encode-target alpha --profile 0 --bit-depth 8 --pix-fmt yuv420 --cpu-used 0 --lossless --monochrome
cavif -i ../avif-sample-images/plum-blossom-small.png -o plum-blossom.avi