controllers-test.rb

get '/test' do
  @user = User.get(1)  # User already created
  pp @user
  
  @test = Test.create(:user => @user)
  pp @test
  
  pp @test.save
  pp @test.errors
end

model-test.rb

class Test
  include DataMapper::Resource
  
  property :id, Serial
  belongs_to :user

end

models-user.rb

class User
  include DataMapper::Resource

  property :id, Serial, :key => true
  property :username, String,
    :required => true,
    :unique   => true,
    :length   => 6..25

  property :password, BCryptHash, :required => true
  attr_accessor :password_confirm
  validates_presence_of :password_confirm
  validates_length_of :password_confirm, :min => 6
  validates_confirmation_of :password, :confirm => :password_confirm

  property :email, String,
    :required => true,
    :unique   => true,
    :format   => :email_address

  property :created,  DateTime
  property :accessed, DateTime
  property :avatar,   Text
  
  has n, :tests
end

server_output

 ~ (0.000520) PRAGMA table_info("users")
 ~ (0.000381) PRAGMA table_info("users")
 ~ (0.000042) PRAGMA table_info("users")
 ~ (0.000031) PRAGMA table_info("users")
 ~ (0.000028) PRAGMA table_info("users")
 ~ (0.000021) PRAGMA table_info("users")
 ~ (0.000021) PRAGMA table_info("users")
 ~ (0.000022) PRAGMA table_info("users")
 ~ (0.000032) PRAGMA table_info("tests")
 ~ (0.000028) PRAGMA table_info("tests")
 ~ (0.000018) PRAGMA table_info("tests")
 ~ (0.000031) PRAGMA table_info("tokens")
 ~ (0.000020) PRAGMA table_info("tokens")
 ~ (0.000025) PRAGMA table_info("tokens")
 ~ (0.000019) PRAGMA table_info("tokens")
 ~ (0.000020) PRAGMA table_info("tokens")
 ~ (0.000106) SELECT "id", "username", "password", "email", "created", "accessed" FROM "users" WHERE "id" = 1 LIMIT 1
#<User @id=1 @username="nhmood" @password="$2a$10$E8B0aB0MWh87jRqiOFQlf.lFKBcvQJWXol6dP8BXdVvKasTzs0oxS" @email="my@email.com" @created=#<DateTime: 2014-04-22T22:46:07-04:00 ((2456771j,9967s,0n),-14400s,2299161j)> @accessed=#<DateTime: 2014-04-22T22:46:07-04:00 ((2456771j,9967s,0n),-14400s,2299161j)> @avatar=<not loaded>>
 ~ (0.000087) SELECT "id", "avatar" FROM "users" WHERE "id" = 1 ORDER BY "id"
 ~ (0.000064) SELECT "id" FROM "users" WHERE "username" = 'nhmood' ORDER BY "id" LIMIT 1
 ~ (0.000072) SELECT "id" FROM "users" WHERE "email" = 'my@email.com' ORDER BY "id" LIMIT 1
#<Test @id=nil @user_id=1>
 ~ (0.000067) SELECT "id" FROM "users" WHERE "username" = 'nhmood' ORDER BY "id" LIMIT 1
 ~ (0.000053) SELECT "id" FROM "users" WHERE "email" = 'my@email.com' ORDER BY "id" LIMIT 1
false
#<DataMapper::Validations::ValidationErrors:0xb90f1888 @resource=#<Test @id=nil @user_id=1>, @errors={}>