Gather UI acceptance test suite requirements
Antora needs a UI acceptance test suite.
- This test suite will test both the UI (via a browser) and the end-to-end site generation.
- The focus of this issue is on gathering requirements for the testing infrastructure. A few sample tests will do.
Currently, end-to-end testing is being handled by the default site generator component and cli application. However, these tests are only asserting on the HTML (using cheerio), not the UI behavior. While these assertions are important, they don't tell the whole story. They also slow down the unit + integration test run because they have to download and integrate the default UI.
We don't want to disable the existing end-to-end tests because then we would be missing coverage. We just need to speed them up. Therefore, we should switch those tests to using a local (fixture) UI bundle. The downloading and integrating of the UI bundle should then be moved to the UI acceptance test suite, which we can then selectively disable without compromising test coverage.
The UI acceptance test suite should use a browser (possibly headless Chrome and/or Firefox) to assert that expected elements are present on the page and that they appear and behave correctly. We may even want to consider visual comparisons in the future.
We should use the demo as the content fixture for these tests. That will also give us coverage of the demo itself so we know it's always working.