我做了一些实验，给出了rails g scaffold foo和这个测试：

require "test_helper"

class FoosControllerTest < ActionDispatch::IntegrationTest
  setup do
    @foo = foos(:one)
  end

  test "should respond with not found" do
    get foo_url('xxxxxx'), as: :json
    assert_response :not_found
    assert_equal({ "status" => 404, "error"=>"Not Found"}, response.parsed_body)
  end
end

在默认设置下，ActiveRecord：：RecordNotFound异常确实不会被异常处理程序捕获，并冒泡到测试中。

Error:
FoosControllerTest#test_should_respond_with_not_found:
ActiveRecord::RecordNotFound: Couldn't find Foo with 'id'=xxxxxx
    app/controllers/foos_controller.rb:63:in `set_foo'
    test/controllers/foos_controller_test.rb:9:in `block in <class:FoosControllerTest>'

在config/environments/test.rb中改变config.consider_all_requests_local和config.action_dispatch.show_exceptions似乎是可行的：

# Show full error reports and disable caching.
config.consider_all_requests_local       = false # was true
config.action_controller.perform_caching = false
config.cache_store = :null_store

# Raise exceptions instead of rendering exception templates.
config.action_dispatch.show_exceptions = true # was false

有了这两个变化，测试通过：

Running 1 tests in a single process (parallelization threshold is 50)
Run options: --seed 27622

# Running:

.

Finished in 0.270401s, 3.6982 runs/s, 7.3964 assertions/s.
1 runs, 2 assertions, 0 failures, 0 errors, 0 skips

然而，这样做可能不是最好的主意，因为应用程序中的异常通常会导致您的测试提前退出。一个简单的解决方法是使用assert_raise来捕获异常，当它冒泡到测试时：

require "test_helper"

class FoosControllerTest < ActionDispatch::IntegrationTest
  setup do
    @foo = foos(:one)
  end

  test "should respond with not found" do
    assert_raise(ActiveRecord::RecordNotFound) do
      get foo_url('xxxxxx'), as: :json
      assert_response :not_found
      assert_equal({ "status" => 404, "error"=>"Not Found"}, response.parsed_body)
    end
  end
end