Sometimes, we are unable to take a frame snapshot. The most common
example would be "frame is stuck during the navigation in Chromium",
where we cannot evaluate until the frame is done navigating.
In this case, use all other frames and just stub the failing ones
with "Snapshot is not available". Chances are, noone will even see
this frame because it's an invisible tracking iframe.
We used to do fetch() to decode the file buffer. However, this is
blocked by strict CSP policy. Instead, we can use explicit
string -> bytes conversion, and trade performance for CSP compliance.
We currently launch and then close the empty browser. This does not
trigger many codepaths related to web page process creation and
browser context.
With opening and navigating a page, we do a more real-life test.
This exposes an issue from #3740.
This is a large rework of selectors:
- Each BrowserContext now has a separate Selectors instance that has its own registrations.
Most of them share a single sharedSelectors instance, but contexts created for a connected
browser have their own instance.
- Connected browser now gets a RemoteBrowser object that encapsulates Selectors and Browser.
This Selectors object is registered with the api selectors.
- Public selectors.register api iterates over all registered Selectors channels
and registers in each of them.
- createSelector testing method migrated to ElementHandle._createSelectorForTest.
This introduces basic tracing enabled in our tests.
What is captured:
- network resources;
- snapshots at the start of most actions;
- snapshot after the test failure.
How this integrates with test runner:
- context fixture calls private method context._initSnapshotter() and uses Tracer to trace all events;
- all tests share a single test-results/trace-storage directory to store blobs;
- each test has its own trace file.
- npm run show-trace opens a bare-minimum trace viewer that renders snapshots.
