Resolves#14255.
PNGs should be preferred as they are deterministic, but increasing this
limit should be fine for JPEG users. (Looking through jpeg-js source code, the actual memory allocation is based on the size of the image—so unless a user is hitting this limit already—this should not impact the memory consumption of Playwright.
This patch aligns the strategies that are used to generate new
screnshot expectations and to compare screenshot expectations against
baseline.
With this patch, `toHaveScreenshot` will:
- when generating a new expectation: will wait for 2 consecutive
screenshots to match and accept the last one as expectation.
- when given an expectation:
* will compare first screenshot against expectation. If matches,
resolve successfully
* if first screenshot doesn't match, then wait for 2 consecutive
screenshots to match and then compare last screenshot with the
expectation.
An example of a new detailed call log:
```
1) a.spec.ts:3:1 › should work ===================================================================
Error: Screenshot comparison failed:
20000 pixels (ratio 0.03 of all image pixels) are different
Call log:
- expect.toHaveScreenshot with timeout 5000ms
- verifying given screenshot expectation
- fast-path: checking first screenshot to match expectation
- taking page screenshot
- disabled all CSS animations
- waiting for fonts to load...
- fonts in all frames are loaded
- fast-path failed: first screenshot did not match expectation - 20000 pixels (ratio 0.03 of all image pixels) are different
- waiting for 2 consecutive screenshots to match
- waiting 100ms before taking screenshot
- taking page screenshot
- disabled all CSS animations
- waiting for fonts to load...
- fonts in all frames are loaded
- 2 consecutive screenshots matched
- final screenshot did not match expectation - 20000 pixels (ratio 0.03 of all image pixels) are different
- 20000 pixels (ratio 0.03 of all image pixels) are different
Expected: /Users/andreylushnikov/tmp/test-results/a-should-work/should-work-1-expected.png
Received: /Users/andreylushnikov/tmp/test-results/a-should-work/should-work-1-actual.png
Diff: /Users/andreylushnikov/tmp/test-results/a-should-work/should-work-1-diff.png
3 | test('should work', async ({ page }) => {
4 | await page.goto('file:///Users/andreylushnikov/prog/playwright/tests/assets/rotate-z.html');
> 5 | await expect(page).toHaveScreenshot();
| ^
6 | });
7 |
```
