Make the test environment show rescuable exceptions in responses

[jdufresne]

Background

During integration tests, it is desirable for the application to respond as closely as possible to the way it would in production. This improves confidence that the application behavior acts as it should.

In Rails tests, one major mismatch between the test and production environments is that exceptions raised during an HTTP request (e.g. ActiveRecord::RecordNotFound) are re-raised within the test rather than rescued and then converted to a 404 response.

Setting config.action_dispatch.show_exceptions to true will make the test environment act like production, however, when an unexpected internal server error occurs, the test will be left with a opaque 500 response rather than presenting a useful stack trace. This makes debugging more difficult.

This leaves the developer with choosing between higher quality integration tests or an improved debugging experience on a failure.

I propose that we can achieve both.

Solution

Change the configuration option config.action_dispatch.show_exceptions from a boolean to one of 3 values: :all, :rescuable, :none. The values :all and :none behaves the same as the previous true and false respectively. What was previously true (now :all) continues to be the default for non-test environments.

The new :rescuable value is the new default for the test environment. It will show exceptions in the response only for rescuable exceptions as defined by ActionDispatch::ExceptionWrapper.rescue_responses. In the event of an unexpected internal server error, the exception that caused the error will still be raised within the test so as to provide a useful stack trace and a good debugging experience.