Add notifications of severed relationships (#27511)

spec/models/relationship_severance_event_spec.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe RelationshipSeveranceEvent do
+  let(:local_account)  { Fabricate(:account) }
+  let(:remote_account) { Fabricate(:account, domain: 'example.com') }
+  let(:event)          { Fabricate(:relationship_severance_event) }
+
+  describe '#import_from_active_follows!' do
+    before do
+      local_account.follow!(remote_account)
+    end
+
+    it 'imports the follow relationships with the expected direction' do
+      event.import_from_active_follows!(local_account.active_relationships)
+
+      relationships = event.severed_relationships.to_a
+      expect(relationships.size).to eq 1
+      expect(relationships[0].account).to eq local_account
+      expect(relationships[0].target_account).to eq remote_account
+    end
+  end
+
+  describe '#import_from_passive_follows!' do
+    before do
+      remote_account.follow!(local_account)
+    end
+
+    it 'imports the follow relationships with the expected direction' do
+      event.import_from_passive_follows!(local_account.passive_relationships)
+
+      relationships = event.severed_relationships.to_a
+      expect(relationships.size).to eq 1
+      expect(relationships[0].account).to eq remote_account
+      expect(relationships[0].target_account).to eq local_account
+    end
+  end
+
+  describe '#affected_local_accounts' do
+    before do
+      event.severed_relationships.create!(local_account: local_account, remote_account: remote_account, direction: :active)
+    end
+
+    it 'correctly lists local accounts' do
+      expect(event.affected_local_accounts.to_a).to contain_exactly(local_account)
+    end
+  end
+end