tests/test-worker.t

obsolescence: add test for the "branch replacement" logic during push, case B7

Mercurial checks for the introduction of new heads on push. Evolution comes
into play to detect if existing branches on the server are being replaced by
some of the new one we push.

This changeset adds test for the improved "branch replacement" logic introduce
in an earlier commits. This tests initially lived in the evolve extensions.
Since we now have the code handling this logic in core, it make sense to have
the tests in core too.

See inline documentation for details about the test case added in this
changeset.

Test UI worker interaction

  $ cat > t.py <<EOF
  > from __future__ import absolute_import, print_function
  > from mercurial import (
  >     cmdutil,
  >     ui as uimod,
  >     worker,
  > )
  > def runme(ui, args):
  >     for arg in args:
  >         ui.status('run\n')
  >         yield 1, arg
  > cmdtable = {}
  > command = cmdutil.command(cmdtable)
  > @command('test', [], 'hg test [COST]')
  > def t(ui, repo, cost=1.0):
  >     cost = float(cost)
  >     ui.status('start\n')
  >     runs = worker.worker(ui, cost, runme, (ui,), range(8))
  >     for n, i in runs:
  >         pass
  >     ui.status('done\n')
  > EOF
  $ abspath=`pwd`/t.py
  $ hg init

Run tests with worker enable by forcing a heigh cost

  $ hg --config "extensions.t=$abspath" test 100000.0
  start
  run
  run
  run
  run
  run
  run
  run
  run
  done

Run tests without worker by forcing a low cost

  $ hg --config "extensions.t=$abspath" test 0.0000001
  start
  run
  run
  run
  run
  run
  run
  run
  run
  done