Add feature tests for real-time pipeline#show and merge_requests#show

Description

Recently Gitlab added a feature of rendering pipeline-mini-graph in real-time for merge request window. And those real-time processing will be adopted little by little into each page, such as pipeline index/show page. However, the test has not fully prepared yet, and the needs would be on demand in the future.

We also need a dedicated mock class of pipeline processing.

e.g.

scenario '...' do
  runner = create_runner(pipeline) # create a runner which processes the pipeline
  expect(page).to have_selector(...)

  # Process the first stage
  runner.start # stage: 'build' - job1 running
  expect(page).to have_selector(...)

  # Finishes the first stage
  runner.proceed_with(:success) # stage: 'build' - job1 success -> stage: 'test' - job2 running
  expect(page).to have_selector(...)
end

(NOTE: This class design may be changed)

Proposal

Add feature tests with a dedicated mock class of pipeline processing
The MR should reproduce

Check the bug will be fixed by https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11087

Links / references

Real-time && feature-tests missing

pipeline#show
merge_requests#show

/cc @grzesiek @godfat

Edited Jul 27, 2020 by Jason Yavorsky