[Feature]: Support omitBackground in toHaveScreenshot in playwright config

[wsuwt]

🚀 Feature Request

Support omitBackground in expect > toHaveScreenshot in playwright config.

Currently, it will throw a TypeScript error when setting omitBackground to playwright config. It would be great if there was somehow a way to set this globally without having to do it in each assertion.

Example

export default defineConfig({
    expect: {
      toHaveScreenshot: {
        omitBackground: true,
    }
  }
})

Motivation

A flag to globally omit background when screenshot is taken.

[Skn0tt]

Hi, could you elaborate on why you're using omitBackground in your snapshot tests? We originally added it for printing screenshots, not for testing, so it's interesting to learn more about new usecases.

[wsuwt]

Hi, I'm using snapshot testing along with component testing. I observed minor rendering differences between each run which is totally expected but I was thinking if background can be omitted, I may be able to improve the accuracy of the test cases by eliminating spaces around the component screenshot.

[Skn0tt]

Minor differences are to be expected - browser rendering is just inherently indeterministic. Omitting background will only help partially. You'll likely get more stable results by changing maxDiffPixelRatio.

[wsuwt]

Thanks for the insight and clarification.