You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: test_trace.rb
    path of file: ./repos/opal/test/opal/promisev2
    
    the code of the file until where you have to start completion: require 'test/unit'
require 'promise/v2'

class TestPromiseTrace < Test::Unit::TestCase
  def test_calls_the_block_with_all_the_previous_results
    x =
    
  def test_works_after_a_when
    x = 42

    PromiseV2.value(1).then {
      PromiseV2.when PromiseV2.value(2), PromiseV2.value(3)
    }.trace {|a, b|
      #x = a + b[0] + b[1]
      x = "#{a},#{b}"
    }.always { assert_equal(x, "1,native") } # 6
  end