Add validations and unit test to Domain model

app/models/domain.rb

@@ -2,6 +2,8 @@ class Domain < ApplicationRecord
   serialize :groups, coder: YAML, type: Array
   before_save :clean_groups
 
+  validates :fqdn, :owner, presence: true
+
   def clean_groups
     self.groups = groups.sort.uniq
   end

test/models/domain_test.rb

@@ -0,0 +1,40 @@
+# test/models/cert_issue_request_test.rb
+require "test_helper"
+
+class DomainTest < ActiveSupport::TestCase
+  def setup
+    @attributes = {
+      fqdn: "example4.com",
+      owner: "[email protected]",
+    }
+    @domain = Domain.new(@attributes)
+  end
+
+  test "#new should set attributes from attributes argument" do
+    @attributes.each do |key, value|
+      assert_equal value, @domain.send(key), "Attribute #{key} was not set correctly"
+    end
+  end
+
+  test "#valid? should be valid with valid attributes" do
+    assert @domain.valid?
+  end
+
+  test "#valid? should require an fqdn" do
+    @domain.fqdn = nil
+    assert_not @domain.valid?
+    assert_includes @domain.errors[:fqdn], "can't be blank"
+  end
+
+  test "#valid? should require an owner" do
+    @domain.owner = nil
+    assert_not @domain.valid?
+    assert_includes @domain.errors[:owner], "can't be blank"
+  end
+
+  test "before_save should sort and dedupe groups" do
+    @domain.groups = [ "two", "two", "one" ]
+    @domain.save
+    assert_equal [ "one", "two" ], @domain.groups
+  end
+end