Add tests for SessionActivation (#5668)

* Fabricate SessionActivation

not only user_id but user association.

* Add tests for SessionActivation

spec/fabricators/session_activation_fabricator.rb

 Fabricator(:session_activation) do
-  user_id    1
+  user
   session_id "MyString"
 end

spec/models/session_activation_spec.rb

+# frozen_string_literal: true
+
 require 'rails_helper'
 
 RSpec.describe SessionActivation, type: :model do
-  pending "add some examples to (or delete) #{__FILE__}"
+  describe '#detection' do
+    let(:session_activation) { Fabricate(:session_activation, user_agent: 'Chrome/62.0.3202.89') }
+
+    it 'sets a Browser instance as detection' do
+      expect(session_activation.detection).to be_kind_of Browser::Chrome
+    end
+  end
+
+  describe '#browser' do
+    before do
+      allow(session_activation).to receive(:detection).and_return(detection)
+    end
+
+    let(:detection)          { double(id: 1) }
+    let(:session_activation) { Fabricate(:session_activation) }
+
+    it 'returns detection.id' do
+      expect(session_activation.browser).to be 1
+    end
+  end
+
+  describe '#platform' do
+    before do
+      allow(session_activation).to receive(:detection).and_return(detection)
+    end
+
+    let(:session_activation) { Fabricate(:session_activation) }
+    let(:detection)          { double(platform: double(id: 1)) }
+
+    it 'returns detection.platform.id' do
+      expect(session_activation.platform).to be 1
+    end
+  end
+
+  describe '.active?' do
+    subject { described_class.active?(id) }
+
+    context 'id is absent' do
+      let(:id) { nil }
+
+      it 'returns nil' do
+        is_expected.to be nil
+      end
+    end
+
+    context 'id is present' do
+      let(:id) { '1' }
+      let!(:session_activation) { Fabricate(:session_activation, session_id: id) }
+
+      context 'id exists as session_id' do
+        it 'returns true' do
+          is_expected.to be true
+        end
+      end
+
+      context 'id does not exist as session_id' do
+        before do
+          session_activation.update!(session_id: '2')
+        end
+
+        it 'returns false' do
+          is_expected.to be false
+        end
+      end
+    end
+  end
+
+  describe '.activate' do
+    let(:options) { { user: Fabricate(:user), session_id: '1' } }
+
+    it 'calls create! and purge_old' do
+      expect(described_class).to receive(:create!).with(options)
+      expect(described_class).to receive(:purge_old)
+      described_class.activate(options)
+    end
+
+    it 'returns an instance of SessionActivation' do
+      expect(described_class.activate(options)).to be_kind_of SessionActivation
+    end
+  end
+
+  describe '.deactivate' do
+    context 'id is absent' do
+      let(:id) { nil }
+
+      it 'returns nil' do
+        expect(described_class.deactivate(id)).to be nil
+      end
+    end
+
+    context 'id exists' do
+      let(:id) { '1' }
+
+      it 'calls where.destroy_all' do
+        expect(described_class).to receive_message_chain(:where, :destroy_all)
+          .with(session_id: id).with(no_args)
+
+        described_class.deactivate(id)
+      end
+    end
+  end
+
+  describe '.purge_old' do
+    it 'calls order.offset.destroy_all' do
+      expect(described_class).to receive_message_chain(:order, :offset, :destroy_all)
+        .with('created_at desc').with(Rails.configuration.x.max_session_activations).with(no_args)
+
+      described_class.purge_old
+    end
+  end
+
+  describe '.exclusive' do
+    let(:id) { '1' }
+
+    it 'calls where.destroy_all' do
+      expect(described_class).to receive_message_chain(:where, :destroy_all)
+        .with('session_id != ?', id).with(no_args)
+
+      described_class.exclusive(id)
+    end
+  end
 end