How do you test custom Bugsnag meta_data in Ruby?

Question

How do you test custom Bugsnag meta_data (in Ruby, with Rspec)?

The code that I want to test:

def do_something
  thing_that_could_error
rescue => e
  Bugsnag.notify(e) do |r|
    r.meta_data = { my_extra_data: "useful info" }
  end
end

The test I want to write:

context "when there's an error" do
  it "calls Bugsnag with my special metadata" do
    expect(Bugsnag).to receive(:notify) # TODO test meta_data values contain "my useful info"
    expect do
      do_something() # exception is thrown and rescued and sent to Bugsnag
    end.not_to raise_error
  end
end

I am using:

Ruby 2.6.6
Rspec 3.9.0
Bugsnag 6.17.0 https://rubygems.org/gems/bugsnag

The data inside of the meta_data variable is considerably more complicated than in this tiny example, which is why I want to test it. In a beautiful world, I would extract that logic to a helper and test the helper, but right now it is urgent and useful to test in situ.

I've been looking at the inside of the Bugsnag gem to figure this out (plus some Rspec-fu to capture various internal state and returned data) but at some point it's a good idea to ask the internet.

score 2 · Accepted Answer · answered Jan 08 '21 at 10:26

Since the metadata is complicated, I'd suggest simplifying it:

def do_something
  thing_that_could_error
rescue => e
  Bugsnag.notify(e) do |r|
    r.meta_data = error_metadata(e, self, 'foo')
  end
end

# I assumed that you'd like to pass exception and all the context
def error_metadata(e, object, *rest)
  BugsnagMetadataComposer.new(e, object, *rest).metadata
end

So now you can have a separate test for BugsnagMetadataComposer where you have full control (without mocking) over how you initialize it, and test for metadata output.

Now you only have to test that BugsnagMetadataComposer is instantiated with the objects you want, metadata is called and it returns dummy hash:

let(:my_exception) { StandardError.new } 
let(:mock_metadata) { Hash.new } 

before do
  # ensure thing_that_could_error throws `my_exception`
expect(BugsnagMetadataComposer)
  .to receive(new)
  .with(my_exception, subject, anything)
  .and_return(mock_metadata)
end

And the hard part, ensure that metadata is assigned. To do that you can cheat a little and see how Bugsnag gem is doing it

Apparently there's something called breadcrumbs:

  let(:breadcrumbs) { Bugsnag.configuration.breadcrumbs }

Which I guess has all the Bugsnag requests, last one on top, so you can do something similar to https://github.com/bugsnag/bugsnag-ruby/blob/f9c539670c448f7f129a3f8be7d412e2e824a357/spec/bugsnag_spec.rb#L36-L40

specify do 
  do_something()

  expect(breadcrumbs.last.metadata).to eq(expected_metadata)
end

And for clarity, the whole spec would look a bit like this:

let(:my_exception) { StandardError.new } 
let(:mock_metadata) { Hash.new } 

before do
  # ensure thing_that_could_error throws `my_exception`
  expect(BugsnagMetadataComposer)
    .to receive(new)
    .with(my_exception, subject, anything)
    .and_return(mock_metadata)
end

specify do 
  do_something()

  expect(breadcrumbs.last.metadata).to eq(expected_metadata)
end

How do you test custom Bugsnag meta_data in Ruby?

1 Answers1