CODEWITHSUNDEEP
ruby-on-railsrubyexceptiontestingtestcase
Magne
Magne

Reputation: 17223

How to test whether any exception was rescued?

Is there a way to find out whether any exception was raised and rescued during the execution of some code?

Preferably in tests written with ActiveSupport::TestCase and not RSpec

Is there any global ruby exception stack or something, which I could check?

Upvotes: 2

Views: 618

Answers (2)

ndnenkov
ndnenkov

Reputation: 36100

As clarified in the comments, OP needed it for debug purposes as opposed to write tests with it.

Kernel#set_trace_func lets you intercept low level events such as an error being raised:

set_trace_func(proc do |event, *_|
  puts 'Raised!' if event == 'raise'
end)

raise 'Oh, no!' rescue :foo

You can run #set_trace_func before the code you were trying to debug. If no exception was raised, but a raise was registered by the hook - someone rescued it.

This can create some noise depending on what you are executing. Fortunately, you can filter it down by file and line:

set_trace_func(proc do |event, file, line, *_|
  if event == 'raise' && file == 'test.rb' && line == 42
    puts "Raised on #{file}:#{line}!"
  end
end)

It even gives you the binding, so you can drop down a debugger:

require 'irb'

set_trace_func(proc do |event, *_, error_binding, _|
  error_binding.irb if event == 'raise'
end)

def foo
  bar = 42
  raise 'Oh, no!' rescue :baz
end

foo

# Opens an irb
# > bar # => 42

Upvotes: 1

eiko
eiko

Reputation: 5345

If you want to be a monster, you can instrument the errors themselves:

class StandardError
  @@called = false

  def initialize
    @@called = true
    super
  end

  def self.called
    @@called
  end
end

#test it out like so:

def raise_arg_error
  raise ArgumentError
rescue
end

puts ArgumentError.called #false
raise_arg_error
puts ArgumentError.called #true

Great for ad hoc sanity checks. Terrible for production code.

Upvotes: 7

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