I have worked this week on testing my controller for my Rails application, and I found something interesting about strong parameters and my results, of course I would like to dig deeper and learn more about why this difference shows in my tests.

First I wanted to create a test for my POST method on one of my controllers so I wrote this first test:

let(:meeting) { create(:meetings_list) }

....
  describe 'POST #create' do
    context 'when user is registered' do
      login_user
      it 'should save the new meeting list with proper attributes' do
        expect do
          post(:create, params: { meetings_list: {
                 title: meeting.title,
                 responsible: meeting.responsible
               } })
        end.to change { MeetingsList.count }.by(2)
      end

When I first wrote it I used the count change by 1 on the last line and it failed, the test indicated 2 was the final count, which I did not understood why. So I went back to my factory and checked:

FactoryBot.define do
  factory :meetings_list do
    title       { Faker::Team.name }
    responsible { Faker::TvShows::SouthPark.character }
  end

  factory :invalid_meeting, parent: :meetings_list do
    title { nil }
  end

  factory :meetings_item do
    meetings_list
    date   { 'Date of Today' }
    reason { 'Spende' }
    amount { 22 }
  end
end

So this lead me to write the test with another method included in factorybot, attributes_for, which became helpful and less code was also written. I am not sure if this is more o less explicit but It worked so far. I would like to have some feedback, since tests are supposed to be explicit and simple to read or at least that is what I am aiming for.

 describe 'POST #create' do
    context 'when user is registered' do
      login_user
      it 'should save the new meeting list with proper attributes' do
        expect do
          post(:create, params: { meetings_list:
                                  FactoryBot.attributes_for(:meetings_list)})
        end.to change { MeetingsList.count }.by(1)
      end

Now it passes to green, only one "meeting_list" was created and the test pass with success. What was making the two "meetings_list" to be created before?