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americanexpress / jest-image-snapshot

✨ Jest matcher for image comparisons. Most commonly used for visual regression testing.
Apache License 2.0
3.81k stars 197 forks source link

Allow custom comparisonMethod #326

Open kolodny opened 1 year ago

kolodny commented 1 year ago

I'd like to try out the ssim-cie94 method of @playwright/test. To do that I'd need to be able to provide a custom function to comparisonMethod (as opposed to just the two string options: 'pixelmatch' | 'ssim'). I think this property can accept a function and just execute that function with the same arguments it's already using for the other two methods https://github.com/americanexpress/jest-image-snapshot/blob/c3cfd12be15eb92f0213ab91cf2cc071c909bacc/src/diff-snapshot.js#L225

Essentially it'll change to this

- const comparisonFn = comparisonMethod === 'ssim' ? ssimMatch : pixelmatch;
+ const comparisonFn = typeof comparisonMethod === 'function' ? comparisonMethod :
+   comparisonMethod === 'ssim' ? ssimMatch : pixelmatch;

This will also make the library more robust to handle other custom diffing strategies moving forward.