undefined method `file_fixture_path' after upgrade to ruby 3 and rails 6.1

After upgrade to ruby 3 and rails 6.1 my tests break on the line

subject.avatar.attach(fixture_file_upload(Rails.root.join('spec', 'fixtures', 'images', 'avatar.jpg')))

with:

NoMethodError:
        undefined method `file_fixture_path' for RSpec::Rails::FixtureFileUploadSupport::RailsFixtureFileWrapper:Class
        Did you mean?  fixture_path

the error stack points to webmock-3.11.0/lib/webmock/rspec.rb:37

Any suggestions how to debug it?

Ran into the same error, but had to solve it differently as the post in a request spec doesn't accept the object returned by file_fixture.

Including include ActionDispatch::TestProcess::FixtureFile in my request solved it for me.

RSpec.describe "Attachments", type: :request do
  include Rack::Test::Methods
  include ActionDispatch::TestProcess::FixtureFile
  #...
    expect {
      file = fixture_file_upload("image.jpg", "image/jpeg", :binary)
      post collection_work_attachments_path(collection, work), {attachment: {file: file, name: image_name, visibility: [:admin]}}
    }.to change(Attachment, :count).by(1)
  #...
end