unhandled_exception_formatter

UnhandledExceptionFormatter

Custom RSpec formatter to output unhandled exception.

Background

To rescue exceptions raised from application, we often tend to write code like:

class ApplicationController < ActionController::Base
  rescue_from ::Exception, :return_internal_server_error
end

While this is convenient, it also masks the actual exceptions. This makes it difficult to debug when unintended exceptions occur during testing.

To mitigate this problem, I thought it would be nice to be able to output uncaught exceptions by custom RSpec formatter.

Installation

Install the gem and add to the application's Gemfile by executing:

bundle add unhandled_exception_formatter

If bundler is not being used to manage dependencies, install the gem by executing:

gem install unhandled_exception_formatter

Usage

Setup

This is an example for Rails application.

class ApplicationController < ActionController::Base
  rescue_from ::Exception, :return_internal_server_error

  if ::Rails.env.test?
    rescue_from ::Exception, :store_unhandled_exception

    before_action :clear_unhandled_exception
  end

  private

  def clear_unhandled_exception
    ::UnhandledExceptionRspecFormatter.unhandled_exception = nil
  end

  # @param [Exception] exception
  # @raise [Exception]
  def store_unhandled_exception(exception)
    ::UnhandledExceptionRspecFormatter.unhandled_exception = exception
    raise exception
  end
end

Run

This formatter only outputs information about unhandled exceptions, so use multiple formatter together to get the output you want.

rspec --format documentation --format UnhandledExceptionFormatter

Note: RSpec automatically require 'unhandled_exception_formatter' from --format option, so there is no need to do this by your side.

Example output

$ rspec --format documentation --format UnhandledExceptionFormatter

UnhandledExceptionFormatter
  example at ./spec/foo_spec.rb:4 (FAILED - 1)
Unhandled exception:
  class:
    RuntimeError
  message:
    example exception
  short backtrace:
    /home/r7kamura/ghq/github.com/r7kamura/unhandled_exception_formatter/spec/foo_spec.rb:5:in `block (2 levels) in <top (required)>'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/example.rb:263:in `instance_exec'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/example.rb:263:in `block in run'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/example.rb:511:in `block in with_around_and_singleton_context_hooks'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/example.rb:468:in `block in with_around_example_hooks'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/hooks.rb:486:in `block in run'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/hooks.rb:624:in `run_around_example_hooks_for'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/hooks.rb:486:in `run'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/example.rb:468:in `with_around_example_hooks'
    /home/r7kamura/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/rspec-core-3.11.0/lib/rspec/core/example.rb:511:in `with_around_and_singleton_context_hooks'

Failures:

  1) UnhandledExceptionFormatter
     Failure/Error: fail
     RuntimeError:
     # ./spec/foo_spec.rb:7:in `block (2 levels) in <top (required)>'

Finished in 0.00088 seconds (files took 0.05668 seconds to load)
1 example, 1 failure

Failed examples:

rspec ./spec/foo_spec.rb:4 # UnhandledExceptionFormatter

The above output is obtained from this code:

# spec/foo_spec.rb
require 'unhandled_exception_formatter'

RSpec.describe UnhandledExceptionFormatter do
  it do
    exception = raise 'example exception' rescue $!
    described_class.unhandled_exception = exception
    fail
  end
end