Add and Remove tests for FollowRequest (#5622)

* Add a test for FollowRequest#authorize!

* Remove tests

There is no need to test
ActiveModel::Validations::ClassMethods#validates.

* Make an alias of destroy! as reject!

Instead of defining the method,
make an alias of destroy! as reject! because of reducing test.

app/models/follow_request.rb

@@ -27,7 +27,5 @@ class FollowRequest < ApplicationRecord
     destroy!
   end
 
-  def reject!
-    destroy!
-  end
+  alias reject! destroy!
 end

spec/models/follow_request_spec.rb

 require 'rails_helper'
 
 RSpec.describe FollowRequest, type: :model do
-  describe '#authorize!'
-  describe '#reject!'
+  describe '#authorize!' do
+    let(:follow_request) { Fabricate(:follow_request, account: account, target_account: target_account) }
+    let(:account)        { Fabricate(:account) }
+    let(:target_account) { Fabricate(:account) }
 
-  describe 'validations' do
-    it 'has a valid fabricator' do
-      follow_request = Fabricate.build(:follow_request)
-      expect(follow_request).to be_valid
-    end
-
-    it 'is invalid without an account' do
-      follow_request = Fabricate.build(:follow_request, account: nil)
-      follow_request.valid?
-      expect(follow_request).to model_have_error_on_field(:account)
-    end
-
-    it 'is invalid without a target account' do
-      follow_request = Fabricate.build(:follow_request, target_account: nil)
-      follow_request.valid?
-      expect(follow_request).to model_have_error_on_field(:target_account)      
+    it 'calls Account#follow!, MergeWorker.perform_async, and #destroy!' do
+      expect(account).to        receive(:follow!).with(target_account)
+      expect(MergeWorker).to    receive(:perform_async).with(target_account.id, account.id)
+      expect(follow_request).to receive(:destroy!)
+      follow_request.authorize!
     end
   end
 end