diff --git a/test/factories/a.rb b/test/factories/a.rb
new file mode 100644
index 0000000..f270d1c
--- /dev/null
+++ b/test/factories/a.rb
@@ -0,0 +1,7 @@
+FactoryGirl.define do
+  factory :a do
+    domain
+    name { generate(:subdomain) }
+    content '1.2.3.4'
+  end
+end
diff --git a/test/factories/domain.rb b/test/factories/domain.rb
new file mode 100644
index 0000000..f216127
--- /dev/null
+++ b/test/factories/domain.rb
@@ -0,0 +1,7 @@
+FactoryGirl.define do
+  sequence(:domain) { |n| "example#{n}.com" }
+  factory :domain do
+    name { generate(:domain) }
+    type 'NATIVE'
+  end
+end
diff --git a/test/factories/record.rb b/test/factories/record.rb
new file mode 100644
index 0000000..558342d
--- /dev/null
+++ b/test/factories/record.rb
@@ -0,0 +1,3 @@
+FactoryGirl.define do
+  sequence(:subdomain) { |n| "sub-#{n}" }
+end
diff --git a/test/factories/soa.rb b/test/factories/soa.rb
new file mode 100644
index 0000000..0cb37d4
--- /dev/null
+++ b/test/factories/soa.rb
@@ -0,0 +1,5 @@
+FactoryGirl.define do
+  factory :soa, class: SOA do
+    serial 3
+  end
+end
diff --git a/test/models/a_test.rb b/test/models/a_test.rb
new file mode 100644
index 0000000..da078ee
--- /dev/null
+++ b/test/models/a_test.rb
@@ -0,0 +1,32 @@
+require 'test_helper'
+
+class ATest < ActiveSupport::TestCase
+  [
+    '0.0.0.0',
+    '1.2.3.4',
+    '255.255.255.255',
+  ].each { |ip|
+    test "content valid #{ip}" do
+      rec = build(:a, content: ip)
+      rec.valid?
+      assert_empty rec.errors[:content], "#{ip} should be valid!"
+    end
+  }
+
+  [
+    'noip',
+    'no ip',
+    '1.2',
+    '1.2.3.4.5',
+    '1.2.3.256',
+    '1.2.3.4/24',
+    '::1',
+  ].each { |ip|
+    test "content invalid #{ip}" do
+      rec = build(:a, content: ip)
+      rec.valid?
+      assert_not_empty rec.errors[:content], "#{name} should be invalid!"
+    end
+  }
+
+end
diff --git a/test/models/domain_test.rb b/test/models/domain_test.rb
new file mode 100644
index 0000000..986fbc4
--- /dev/null
+++ b/test/models/domain_test.rb
@@ -0,0 +1,47 @@
+require 'test_helper'
+
+class DomainTest < ActiveSupport::TestCase
+  def setup
+    @domain = build(:domain)
+  end
+
+  test 'automatic SOA creation' do
+    @domain.save!
+    @domain.reload
+    assert_not_nil @domain.soa
+    assert_equal 1, @domain.soa.serial
+  end
+
+  test 'increment serial on new record' do
+    @domain.save!
+    soa = @domain.soa
+
+    assert_serial_update soa do
+      www = A.new(name: 'www', domain: @domain, content: '1.2.3.4')
+      www.save!
+    end
+  end
+
+  test 'increment serial on record update' do
+    @domain.save!
+    www = A.new(name: 'www', domain: @domain, content: '1.2.3.4')
+    www.save!
+    soa = @domain.soa.reload
+
+    assert_serial_update soa do
+      www.content = '1.2.3.5'
+      www.save!
+    end
+  end
+
+  test 'increment serial on record destroy' do
+    @domain.save!
+    www = A.new(name: 'www', domain: @domain, content: '1.2.3.4')
+    www.save!
+    soa = @domain.soa.reload
+
+    assert_serial_update soa do
+      www.destroy!
+    end
+  end
+end
diff --git a/test/models/soa_test.rb b/test/models/soa_test.rb
new file mode 100644
index 0000000..3ad4cfa
--- /dev/null
+++ b/test/models/soa_test.rb
@@ -0,0 +1,25 @@
+require 'test_helper'
+
+class SOATest < ActiveSupport::TestCase
+  def setup
+    domain = create(:domain)
+    @record = domain.soa
+  end
+
+  test 'bump_serial!' do
+    @record.save!
+
+    assert_serial_update @record do
+      @record.bump_serial!
+    end
+  end
+
+  test 'updating attributes bumps serial' do
+    @record.save!
+
+    assert_serial_update @record do
+      @record.contact = 'admin@example.com'
+      @record.save!
+    end
+  end
+end
diff --git a/test/support/assertions.rb b/test/support/assertions.rb
new file mode 100644
index 0000000..b672f57
--- /dev/null
+++ b/test/support/assertions.rb
@@ -0,0 +1,13 @@
+module Assertions
+
+  def assert_serial_update(soa, message=nil)
+    soa.reload
+    assert_difference 'soa.serial', 1, message do
+      yield
+      soa.reload
+    end
+  end
+
+end
+
+ActiveSupport::TestCase.include Assertions