Buildkite supports showing images in log output, which is incredibly awesome for application tests that can produce screenshots. It would be awesome if Circle supported this.
Depending on what you’re using to run tests, you should be able to configure your test runner to produce screenshots. If those are stored by the test runner, you can then upload those screenshots as artifacts.
If you are stuck, just echo the image out in Base64, with an easily detectable header/footer text mark. You can then easily detect this and parse it using a client-side script. I just copy+paste the Base64 data, but I expect you could fetch it from the API if required.
Yes, you can upload a bunch of image files as artifacts. But they are out of context. There is the build log, which lists the tests that were run and whether they passed or not. That’s where I would want to see a screenshot for each test, like on Buildkite. Finding the right image in artifacts and downloading it is cumbersome.