fix(test runner): avoid internal error for step end without begin
Consider the following scenario:
- Test finishes and starts tearing down fixtures.
- Fixture teardown starts a step S and then times out.
- We declare the test finished (with timeout).
- Dispatcher shuts down the worker and spins a new one for a retry.
Additionally, it clears steps information for the test to be
ready for the new retry. Step S information is lost.
- Meanwhile, during worker teardown, the step S does
actually finish (usually with an error), and we send stepEnd for S.
- Dispatcher does not know what to do with step S end and
prints an internal error.
The fix is to ignore certain messages from the shutting down worker that failed.
- Uses some auto fixtures to set default options and instrumentation on BrowserType.
- Moves screenshot, trace and video to worker-scoped fixtures.
- Throws in page/context when used from beforeAll/afterAll.
- Plumbs around BrowserType to be accessible from Browser and BrowserContext.
- `TestResult.startTime`
- `Suite.location` is optional now
- `Test.status()` renamed to `Test.outcome()` to differentiate against a
`Test.expectedStatus` and `TestResult.status` of the different type.
This makes our suite structure the following:
```
Root(title='') > Project(title=projectName) > File(title=relativeFilePath) > ...suites > test
```
Removed `fullTitle()` because it is not used directly by anyone.
Default reporters now report each test as
```
[project-name] › relative/file/path.spec.ts:42:42 › suite subsuite test title
```
We now have Suites and Tests. When running multiple projects the whole
suite is cloned for each project. Same happens for repeatEach.
This simplifies the reporters API, but there is still room for improvement.
JSON reporter continues to produce old json output.
