The specs were relying a lot on mock and stubs. I suspect that under certain circumstances it didn't play well with fabricators and we ended up with the stub of another spec causing this kind of error:
```
1) Chat::AutoJoinChannelBatch.call when arguments are valid when channel is found when more than one membership is created publishes an event
Failure/Error: subject(:result) { described_class.call(params) }
Mocha::ExpectationError:
unexpected invocation: Chat::Publisher.publish_new_channel(#<Chat::CategoryChannel:0x39b840>, #<User::ActiveRecord_Relation:0x39b868>)
unsatisfied expectations:
- expected exactly once, invoked never: Chat::Publisher.publish_new_channel(#<Chat::CategoryChannel:0x39b890>, [#<User:0x39b8b8>, #<User:0x39b8e0>])
satisfied expectations:
- allowed any number of times, invoked once: Chat::Action::CreateMembershipsForAutoJoin.call(has_entries({:channel => #<Chat::CategoryChannel:0x39b890>, :contract => instance_of(Chat::AutoJoinChannelBatch::Contract)}))
- allowed any number of times, invoked never: Chat::ChannelMembershipManager.new(#<Chat::CategoryChannel:0x39b890>)
- allowed any number of times, invoked never: #<Mock:0x39b930>.recalculate_user_count(any_parameters)
# ./plugins/chat/app/services/chat/auto_join_channel_batch.rb:65:in `publish_new_channel'
# ./plugins/chat/app/services/service/base.rb:118:in `instance_exec'
# ./plugins/chat/app/services/service/base.rb:118:in `call'
# ./plugins/chat/app/services/service/base.rb:368:in `block in run!'
# ./plugins/chat/app/services/service/base.rb:368:in `each'
# ./plugins/chat/app/services/service/base.rb:368:in `run!'
# ./plugins/chat/app/services/service/base.rb:361:in `run'
# ./plugins/chat/app/services/service/base.rb:229:in `call'
# ./plugins/chat/spec/services/chat/auto_join_channel_batch_spec.rb:50:in `block (3 levels) in <main>'
# ./plugins/chat/spec/services/chat/auto_join_channel_batch_spec.rb:110:in `block (6 levels) in <main>'
# ./spec/rails_helper.rb:412:in `block (2 levels) in <top (required)>'
```
The spec is now simplified and shouldn't have this issue anymore.