Stubbing library methods

import_investigations_spec.rb

# Poor specs
# ==========

# Test focus is divided between how library is used and and what is the expected behavior of tested class
describe ImportInvestigations do
  describe '.call' do
    it 'imports investigations to database' do
      stub_const('ImportInvestigations::IMPORT_URL', 'http://gcpd.dev/investigations.json')
      investigations_json = [
        { uid: '123', name: 'Joker: prison escape' }, 
        { uid: 'abc', name: 'Dr. Strange: arsony' }
      ].to_json
      faraday_response = instance_double(Faraday::Response, body: investigations_json)
      allow(Faraday).to receive(:get) { faraday_response }
      
      expect { 
        ImportInvestigations.call
      }.to change { Investigation.count }.from(0).to(2)
      
      expect(Investigation.all).to include(
        have_attributes(uid: '123', suspect_name: 'Joker', case_subject: 'prison escape'),
        have_attributes(uid: 'abc', suspect_name: 'Dr. Strange', case_subject: 'arsony')
      )
      expect(Faraday).to have_received(:get).with('http://gcpd.dev/investigations.json')
    end
  end
end

# Better specs
# ============

# Test does not depend on any particular library being used
describe ImportInvestigations do
  describe '.call' do
    it 'imports investigations to database' do
      stub_const('ImportInvestigations::IMPORT_URL', 'http://gcpd.dev/investigations.json')
      investigations_json = [
        { uid: '123', name: 'Joker: prison escape' }, 
        { uid: 'abc', name: 'Dr. Strange: arsony' }
      ].to_json
      stub_request(:get, "http://gcpd.dev/investigations.json").to_return(status: 200, body: investigations_json)
      
      expect { 
        ImportInvestigations.call
      }.to change { Investigation.count }.from(0).to(2)
      
      expect(Investigation.all).to include(
        have_attributes(uid: '123', suspect_name: 'Joker', case_subject: 'prison escape'),
        have_attributes(uid: 'abc', suspect_name: 'Dr. Strange', case_subject: 'arsony')
      )
    end
  end
end

# Best specs
# ==========

# Retrieval of records is abstracted to facade (that should get own set of tests)
describe ImportInvestigations do
  describe '.call' do
    it 'imports investigations to database' do
      allow(GcpdWrapper).to receive(:get_investigations) { 
        [
          double(uid: '123', suspect_name: 'Joker', case_subject: 'prison escape'),
          double(uid: 'abc', suspect_name: 'Dr. Strange', case_subject: 'arsony')
        ]
      }
      
      expect { 
        ImportInvestigations.call
      }.to change { Investigation.count }.from(0).to(2)
      
      expect(Investigation.all).to include(
        have_attributes(uid: '123', suspect_name: 'Joker', case_subject: 'prison escape'),
        have_attributes(uid: 'abc', suspect_name: 'Dr. Strange', case_subject: 'arsony')
      )
    end
  end
end