Programmable stubs

[danp]

It would be great if I could use a callback to determine how to respond to a stubbed request. For example, I want to return an error if a server certificate named foo is deleted but return a successful response for anything else.

[trevorrowe]

Thanks for the feature request. Depending on what testing framework you use, there are methods to achieve this. For example, using RSpec, you can do the following:

client = Aws::S3::Client.new(stub_responses: true)

# success
allow(client).to receive(:delete_bucket).with(bucket:'aws-sdk').and_return(client.stub_data(:delete_bucket))

# error
allow(client).to receive(:delete_bucket).with(bucket:'aws-sdk-not-empty').and_raise(Aws::S3::Errors::BucketNotEmptyError)

# all other requests will hit the default stubs

Moving this sort of functionality into the client stubbing interface could be helpful as well. The above example can be a bit verbose, and depends on using a mocking/stubbing library. Just sharing it in case it can help.

[danp]

Thanks for the tip. client.stub_data could help.

A downside to that approach is you lose validation on the names of methods you've stubbed (with allow) and the provided args. For example, I could use that to make delete_buckets(bucket_names: ...) or delete_bucket(bucket_name: ...) work but neither of those are valid for real use.

There are probably ways to use rspec/etc to help prevent that but takes care.

[trevorrowe]

I agree. It also prevents the SDK from executing the request stack. Response stubbing very carefully only by-passes the network request. This ensures any handlers or plugins still trigger. The rspec #allow method will short-circuit all of these.

[awood45]

Moved to the feature request backlog.

[janko]

I think this is already possible by passing a Proc as a stub value. I discovered this feature when reading tests for aws-sdk itself, and I just made a PR to document this: #1539.

To take your original example, you should be able to do something like this:

client.stub_responses(:delete_certificate, -> (context) {
  context.params[:certificate_arn] == "foo" ? "YourError" : {...}
})