What exactly do you mean with "edge cases"? For what it's worth, the decoder has been fuzzed[1] and the benchmark suite[2] with 2800 images en-/ and decodes without losing any pixels, as checked by qoibench[3].

[1] https://github.com/phoboslab/qoi/blob/master/qoifuzz.c

[2] https://qoiformat.org/benchmark/

[3] https://github.com/phoboslab/qoi/blob/master/qoibench.c#L440...