Sample helper file for minitest and minitest/spec running with rspec/mocks and simplecov (in a rails engine)

minitest_helper.rb

# Configure Rails Environment
ENV["RAILS_ENV"] = "test"
if ENV['COVERAGE']
  require 'simplecov'
  SimpleCov.start do
    add_filter '/test/'
  end
end

require File.expand_path("../dummy/config/environment.rb",  __FILE__)
require "minitest"
require "minitest/spec"
Minitest.autorun
require 'rspec/mocks'

module MyRSpecMock
  def before_setup
    super
    RSpec::Mocks.setup(self)
  end

  def after_teardown
    begin
      RSpec::Mocks.verify
    ensure
      RSpec::Mocks.teardown
    end
    super
  end
end

class MiniTest::Test
  include MyRSpecMock
end
if ENV['COVERAGE']
  Dir['lib/**/*.rb'].each {|file| load(file); }
end