`Minitest.after_runnable` callbacks to execute after every test class method has been run… it might even work!

after_runnable.rb

# minitest uses Gem.find_files, so this should be somewhere on the load path:
# $LOAD_PATH/minitest/after_runnable_plugin.rb
class Minitest
  class AfterRunnableReporter < AbstractReporter
    def initialize(after_runnable, methods)
      @after_runnable, @methods = after_runnable, methods
    end

    def prerecord(klass, name)
      @methods[klass].delete(name)
    end

    def report(result)
      @after_runnables.reverse_each(&:call) if @methods[result.class].empty?
    end
  end

  class << self
    @@after_runnable = []

    # Minitest.after_suite { eileen.rejoice! }
    def after_runnable(&block)
      @@after_runnable << block
    end

    # Called from within the at_exit autorun, every class/runnable has been loaded.
    # Collects every runnable method within a class, so the reporter can slowly whittle 'em down.
    def plugin_after_suite_init(*)
      reporter << AfterRunnableReporter.new \
        @@after_runnable,
        runnables.map { |runnable| [ runnable, runnable.runnable_methods ] }.to_h
    end
  end
end