add more tests to models

spec/models/follow_spec.rb

@@ -5,4 +5,23 @@ RSpec.describe Follow, type: :model do
   let(:bob)   { Fabricate(:account, username: 'bob') }
 
   subject { Follow.new(account: alice, target_account: bob) }
+
+  describe 'validations' do
+    it 'has a valid fabricator' do
+      follow = Fabricate.build(:follow)
+      expect(follow).to be_valid
+    end
+
+    it 'is invalid without an account' do
+      follow = Fabricate.build(:follow, account: nil)
+      follow.valid?
+      expect(follow).to model_have_error_on_field(:account)
+    end
+
+    it 'is invalid without a target_account' do
+      follow = Fabricate.build(:follow, target_account: nil)
+      follow.valid?
+      expect(follow).to model_have_error_on_field(:target_account)
+    end
+  end
 end