UseCaseMock for testing

[AlexB52]

Testing

When a use case is used in a class to perform an action or query, it can be handy to use a mock for the use case when testing the class.

To do so, require 'use_case_mock' in your specs and use the UseCaseMock class to create the state of the use case after the perform action. This is particularly handy when you want to add errors and keep a stable use case behaviour.
Adding errors to the mock will make the use case failed? but not invalid? and won't raise if perform! is called.

require 'spec_helper'
require 'use_case_mock'

RSpec.describe MyParentClass do

  before do
    use_case = UseCaseMock.new(results: [])
    use_case.errors.add(:base, 'Could not fetch results from 3rd party API')

    allow(MyUseCase).to receive(:perform) { use_case }
  end

  describe '.upload' do
    it 'does something' do
      MyParentClass.upload('/some/random/file.txt')

      # ...
    end
  end
end