[ML] Functional Tests: Extend canvas assertion options.

[walterra]

Summary

Fixes #91450.
Fixes #94854.

Updates the canvas element assertion service:

• Expected colors can now be filtered, useful for example to exclude a known dominant background color.
• Colors themselves will now be asserted with a given tolerance for each RGB channel.
• Anti-aliasing can be turned off to minimize differences in font rendering across systems.
• isColorWithinTolerance() now exposed as part of the canvas element service to make it available for single color checks.

These options in combination should make assertions more stable.

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[walterra]

Further investigating the test failures, the tests are now set up to scroll to the scatterplot before asserting the canvas element, here's a screenshot of the failed test, need to compare against local results next:

[walterra]

@elasticmachine merge upstream

[walterra]

@darnautov @peteharverson yay, this passed finally, ready for review :)

[peteharverson]

Running locally on Windows, I had to edit these values to the following to get it to pass:

            // tick/grid/axis
            { key: '#DDDDDD', value: 50 },
            // lines
            { key: '#98A2B3', value: 30 },
            { key: '#6092C0', value: 10 },
            { key: '#5F92C0', value: 6 },

Before that, this single test was failing with the error

      retry.tryForTime timeout: Error: Color stats for 'mlDFAnalyticsClassificationExplorationRocCurveChart' should be w
ithin tolerance. Expected: '[{"key":"#DDDDDD","value":48},{"key":"#98A2B3","value":32},{"key":"#6092C0","value":10},{"ke
y":"#5F92C0","value":6}]' (got '[{"key":"#DDDDDD","value":54.5920820644334,"withinTolerance":false},{"key":"#98A2B3","va
lue":26.106747876262215,"withinTolerance":false},{"key":"#6092C0","value":9.145696425709247,"withinTolerance":true},{"ke
y":"#5F92C0","value":9.145696425709247,"withinTolerance":true}]')

[walterra]

Thanks, updated in b70f3f9, let's see if it's within the tolerance to still pass CI :)

[peteharverson]

Tested locally and LGTM

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 5c7ef8d
• Storybooks Preview
• Documentation Changes

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
ml	6.4MB	6.4MB	+786.0B

History

• 💚 Build #113949 succeeded e24fbf1
• 💛 Build #113919 was flaky d568b2b
• 💛 Build #113692 was flaky b70f3f9
• 💚 Build #113630 succeeded 65170ec
• 💔 Build #113572 failed 2730771

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @walterra

[walterra]

Yay, flaky test runner passed 42x without failures. https://kibana-ci.elastic.co/job/kibana+flaky-test-suite-runner/1384/