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 |
```
Turns out relying on PWTRAP in stack is not reliable: depending on the
call structure, the stack might be cut unpredictably by Node.js.
This patch removes PWTRAP and instead plumbs explicit stack and
pre-set `apiName` all the way down to `wrapApiCall`.
This patch:
- adds call logs to track screenshot timeouts, e.g. due to
waiting for web fonts
- makes sure all snapshot expectations have `.png` extension
- throws a polite error when given a buffer or a string instead of a
page or a locator
- removes stray NL between error description and call log
- makes sure `apiName` is always correct (and adds a test for it)
