There are quite a few for radial gradients and linear gradients in: https://searchfox.org/mozilla-central/source/layout/reftests/border-image There should be some for conic gradients as well. Also, it might be nice to port those tests to WPT as well, but that's probably separate.
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There are quite a few border-image tests for radial gradients and linear gradients in: https://searchfox.org/mozilla-central/source/layout/reftests/border-image There should be some for conic gradients as well. Also, it might be nice to port those tests to WPT as well, but that's probably separate.