my_test.rb

class MyTestError < StandardError; end

class MyTest
  attr_accessor :test

  def initialize
    @test = {}
  end

  def self.test(description, &block)
    $mytest ||= self.new
    $mytest.test = { description: description, block: block }
    $mytest.execute!
  end

  def assert(r)
    if r == true
      true
    else
      raise MyTestError
    end
  end

  def execute!
    begin
      puts @test[:description]
      self.instance_eval(&@test[:block])
      puts "  --- success"
    rescue MyTestError
      puts "  --- failed"
    end
  end
end

some_tests.rb

require './my_test'

class SomeTests < MyTest
  test "this is a simple test" do
    assert 1 == 1
  end

  test "another simple test" do
    assert 1 != 1
  end
end