Add tests for RemoteFollow (#5651)

* Add tests for RemoteFollow.initialize

* Add tests for RemoteFollow#valid?

* Add tests for RemoteFollow#subscribe_address_for

spec/models/remote_follow_spec.rb

@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe RemoteFollow do
+  describe '.initialize' do
+    let(:remote_follow) { RemoteFollow.new(option) }
+
+    context 'option with acct' do
+      let(:option) { { acct: 'hoge@example.com' } }
+
+      it 'sets acct' do
+        expect(remote_follow.acct).to eq 'hoge@example.com'
+      end
+    end
+
+    context 'option without acct' do
+      let(:option) { {} }
+
+      it 'does not set acct' do
+        expect(remote_follow.acct).to be_nil
+      end
+    end
+  end
+
+  describe '#valid?' do
+    let(:remote_follow) { RemoteFollow.new }
+
+    context 'super is falsy' do
+      module InvalidSuper
+        def valid?
+          nil
+        end
+      end
+
+      before do
+        class RemoteFollow
+          include InvalidSuper
+        end
+      end
+
+      it 'returns false without calling #populate_template and #errors' do
+        expect(remote_follow).not_to receive(:populate_template)
+        expect(remote_follow).not_to receive(:errors)
+        expect(remote_follow.valid?).to be false
+      end
+    end
+
+    context 'super is truthy' do
+      module ValidSuper
+        def valid?
+          true
+        end
+      end
+
+      before do
+        class RemoteFollow
+          include ValidSuper
+        end
+      end
+
+      it 'calls #populate_template and #errors.empty?' do
+        expect(remote_follow).to receive(:populate_template)
+        expect(remote_follow).to receive_message_chain(:errors, :empty?)
+        remote_follow.valid?
+      end
+    end
+  end
+
+  describe '#subscribe_address_for' do
+    before do
+      allow(remote_follow).to receive(:addressable_template).and_return(addressable_template)
+    end
+
+    let(:account)                   { instance_double('Account', local_username_and_domain: local_username_and_domain) }
+    let(:addressable_template)      { instance_double('Addressable::Template') }
+    let(:local_username_and_domain) { 'hoge@example.com' }
+    let(:remote_follow)             { RemoteFollow.new }
+
+    it 'calls Addressable::Template#expand.to_s' do
+      expect(addressable_template).to receive_message_chain(:expand, :to_s).with(uri: local_username_and_domain).with(no_args)
+      remote_follow.subscribe_address_for(account)
+    end
+  end
+end