Generate test_case_started/finished messages at the source

[brasmusson]

Description

Generating messages at the source means that the Runner shall generate test_case_started/finished and test_step_started/finished (at least)

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds new behaviour)

Please add an entry to the relevant section of CHANGELOG.md as part of this pull request.

Note to other contributors

If your change may impact future contributors, explain it here, and remember to update README.md and CONTRIBUTING.md accordingly.

Checklist:

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• Tests have been added for any changes to behaviour of the code
• New and existing tests are passing locally and on CI
• bundle exec rubocop reports no offenses
• CHANGELOG.md has been updated

[luke-hill]

I get the premise of this, but there's a few questions I have regarding how this is used as on first inspection some of these ivars won't change

[brasmusson]

Code wise this pull request is read - the TestCaseStarted/Finished messages and TestStepStarted/Finished messages are emitted by the runner. The runner_spec have not been updated to verify the sending of the messages.
Some complication with this change is that

• the TestCaseFinished message says whether the test case will be retried or not
• the TestStepFinished message uses the BacktraceFilter in case of exception stack traces

The decision to retry or not is handled outside the runner (outside cucumber-ruby-core), and the BacktraceFilter is defined in Cucumber::Formatter in cucumber-ruby. To avoid direct dependencies to cucumber-ruby, the runner have two new arguments so the relevant information can be passed in.

Probably the snippets message should also be emitted by the runner in relation to the TestStepFinishded message, but the generation of the snippets are also handled outside cucumber-ruby-core, so maybe it is the undefined action created from the step matching that should carry snippet data so it can be extracted by the runner.