```ruby
class Yuba::Form::Test < ActiveSupport::TestCase
  form_class = Class.new(Yuba::Form) do
    property :number, type: :int
    property :start_time, type: :date_time
  end

  model_class = Class.new do
    include ActiveModel::Model
    attr_accessor :start_time, :number
  end

  test 'create subclass' do
    Class.new(Yuba::Form)
  end

  test 'property works' do
    form = form_class.new(model_class.new)
    form.number = '1'
    assert_equal form.number, 1
  end

  test "munges multi-param date and time fields into a valid Time attribute" do
    start_time_params = { "start_time(1i)"=>"2000", "start_time(2i)"=>"1", "start_time(3i)"=>"1", "start_time(4i)"=>"12", "start_time(5i)"=>"00" }
    form = form_class.new(model_class.new)
    form.validate(start_time_params)
    assert_equal form.start_time, Time.zone.local(2000, 1, 1, 12, 0)
  end
end
```

Add test for multi assign of date
user
```ruby
class Yuba::Form::Test < ActiveSupport::TestCase
  form_class = Class.new(Yuba::Form) do
    property :number, type: :int
    property :start_time, type: :date_time
  end

  model_class = Class.new do
    include ActiveModel::Model
    attr_accessor :start_time, :number
  end

  test 'create subclass' do
    Class.new(Yuba::Form)
  end

  test 'property works' do
    form = form_class.new(model_class.new)
    form.number = '1'
    assert_equal form.number, 1
  end

  test "munges multi-param date and time fields into a valid Time attribute" do
    start_time_params = { "start_time(1i)"=>"2000", "start_time(2i)"=>"1", "start_time(3i)"=>"1", "start_time(4i)"=>"12", "start_time(5i)"=>"00" }
    form = form_class.new(model_class.new)
    form.validate(start_time_params)
    assert_equal form.start_time, Time.zone.local(2000, 1, 1, 12, 0)
  end

  test "munges multi-param date and date fields into a valid Date attribute" do
    start_time_params = { "start_time(1i)"=>"2000", "start_time(2i)"=>"1", "start_time(3i)"=>"1" }
    form = form_class.new(model_class.new)
    form.validate(start_time_params)
    assert_equal form.start_time, Time.zone.local(2000, 1, 1).to_date
  end
end
```
assistant