mishka_installer plugins in a test run: wait until a list of them is live, register one for the length of a test, and sweep away the test plugins an earlier run left registered.

Waiting for plugins

A plugin registers from its own handle_continue, once mishka_installer says it is ready — and on a slow boot, such as the first run after a recompile, it is not ready yet, so the plugin tries again a second later. By then the first tests have run against events that do not have it: the mail provider is not found, and every test that sends an email fails, once, and passes on the next run. await/2 makes the run start after that second instead of during it.

MishkaCmsCore.Test.Installer.await(MishkaCmsCore.Application.plugins())

It waits on mishka_installer's own :start broadcast for each plugin not started yet, then on MishkaInstaller.Event.EventHandler until no event is waiting to be rebuilt — Event.start/3 queues the rebuild before it broadcasts, so the rebuild is queued by the time the wait sees it.

A plugin for one test

register!/2 registers a module on an event exactly as an extension registers one, rebuilds the event with it, and unregisters it when the test exits. The compiled event is global, so a test using it is async: false.

Plugins that outlived their run

mishka_installer keeps registrations in Mnesia, which is on disk and survives the run that made them — so a suite killed part-way (a crash, a Ctrl-C, a timeout) leaves its plugin registered, and every later run boots with it live. That is invisible and it changes unrelated suites: a leftover builder:components plugin puts an extra card in the palette, and a test asserting on one card sees two. sweep!/1 unregisters every plugin whose module name starts with one of the prefixes given — a project's own test plugins only, since a real plugin belongs to whoever installed it.