Render test passes even though actual image is different from expected.

[NathanMOlson]

The terrain/fog render test passes, even though the actual image is different from the expected image.

Expected:

Actual:

Actual (drawn over a red background to demonstrate the transparent "hole" near the horizon):

Computed Diff:

[HarelM]

The render test are using an external library to compare images: pixelmatch with some configuration.
The configuration is there to prevent false positive test failures.
Feel free to investigate what's causing this...

[NathanMOlson]

Feel free to investigate what's causing this...

The root cause of this bug is that pixelmatch does not detect any difference between white and transparent pixels: mapbox/pixelmatch#26

[HarelM]

Ahh, in that case we should make sure either not to use white or use a solid non-white background.
Another approach we can try is contribute the fix to picelmatch, but I don't have high hopes for this route.

[NathanMOlson]

I submitted a PR to pixelmatch to fix this issue: mapbox/pixelmatch#142. I think it would be a good idea to incorporate this fix, as it may affect other render tests in our test suite.

[HarelM]

Worst case we can patch-package it I guess.
Let's wait a few days and see where this lands.