当在Mac OSX上运行simplecov时，所产生的覆盖率几乎没有意义。
如果运行以下测试：

rails test test/models/channel_test.rb
> 4 runs, 4 assertions, 0 failures, 0 errors, 0 skips
> Coverage report generated for Minitest to /Volumes/[...]/coverage. 0 / 0 LOC (100.0%) covered.

然而，当运行rails test test/models时，图形输出指示test/models/channel_test.rb

require "test_helper" 
class ChannelTest < ActiveSupport::TestCase 
  test "invalid if name not defined" do  
    channel = Channel.new(priority: 1, unit_cost: 1, daily_limit: 9999) 
    assert_not channel.valid?  
    assert_not channel.save, "Saved the channel without a name"
  end

更新我推测可能是测试所选的语法存在缺陷-我添加了补充测试，结果仍然报告

型号3 relevant lines. 0 lines covered and 3 lines missed.

class Channel < ApplicationRecord # red

  validates :name, presence: true # red

end # red

因此，测试通过，但覆盖率结果令人困惑：
a）作为独立测试，覆盖率计数为0/0，而测试通过
B）什么构成miss或相反coverage由a（the？）测试？
test_helper.rb

require 'simplecov'
 SimpleCov.start

ENV['RAILS_ENV'] ||= 'test'
require_relative "../config/environment"
require "rails/test_help"
require 'webmock/minitest'

class ActiveSupport::TestCase
  parallelize(workers: :number_of_processors)

  fixtures :all

  def log_in_as(user, shop)
    post user_session_url, params: { user_id: user.id, active_shop_id: @site.shop_id }
  end

end

更新2根据@BroiSatse的建议，注解掉parallelize(workers: :number_of_processors)允许测量覆盖率。