add more tests to models

spec/models/block_spec.rb

@@ -1,5 +1,22 @@
 require 'rails_helper'
 
 RSpec.describe Block, type: :model do
+  describe 'validations' do
+    it 'has a valid fabricator' do
+      block = Fabricate.build(:block)
+      expect(block).to be_valid
+    end
 
+    it 'is invalid without an account' do
+      block = Fabricate.build(:block, account: nil)
+      block.valid?
+      expect(block).to model_have_error_on_field(:account)
+    end
+
+    it 'is invalid without a target_account' do
+      block = Fabricate.build(:block, target_account: nil)
+      block.valid?
+      expect(block).to model_have_error_on_field(:target_account)
+    end
+  end
 end