Active Model Lint Tests

You can test whether an object is compliant with the Active Model API by including ActiveModel::Lint::Tests in your TestCase. It will include tests that tell you whether your object is fully compliant, or if not, which aspects of the API are not implemented.

These tests do not attempt to determine the semantic correctness of the returned values. For instance, you could implement valid? to always return true, and the tests would pass. It is up to you to ensure that the values are semantically meaningful.

Objects you pass in are expected to return a compliant object from a call to to_model. It is perfectly fine for to_model to return self.

Instance Public methods

Errors Testing

Returns an object that has :[] and :full_messages defined on it. See below for more details.

Returns an Array of Strings that are the errors for the attribute in question. If localization is used, the Strings should be localized for the current locale. If no error is present, this method should return an empty Array.

# File activemodel/lib/active_model/lint.rb, line 91
def test_errors_aref
  assert model.respond_to?(:errors), "The model should respond to errors"
  assert model.errors[:hello].is_a?(Array), "errors#[] should return an Array"

Returns an Array of all error messages for the object. Each message should contain information about the field, if applicable.

# File activemodel/lib/active_model/lint.rb, line 98
def test_errors_full_messages
  assert model.respond_to?(:errors), "The model should respond to errors"
  assert model.errors.full_messages.is_a?(Array), "errors#full_messages should return an Array"


Model.model_name must return a string with some convenience methods as :human and :partial_path. Check ActiveModel::Naming for more information.

# File activemodel/lib/active_model/lint.rb, line 72
def test_model_naming
  assert model.class.respond_to?(:model_name), "The model should respond to model_name"
  model_name = model.class.model_name
  assert_kind_of String, model_name
  assert_kind_of String, model_name.human
  assert_kind_of String, model_name.partial_path
  assert_kind_of String, model_name.singular
  assert_kind_of String, model_name.plural

Responds to persisted?

Returns a boolean that specifies whether the object has been persisted yet. This is used when calculating the URL for an object. If the object is not persisted, a form for that object, for instance, will be POSTed to the collection. If it is persisted, a form for the object will be PUT to the URL for the object.

# File activemodel/lib/active_model/lint.rb, line 62
def test_persisted?
  assert model.respond_to?(:persisted?), "The model should respond to persisted?"
  assert_boolean model.persisted?, "persisted?"

Responds to to_key

Returns an Enumerable of all (primary) key attributes or nil if model.persisted? is false

# File activemodel/lib/active_model/lint.rb, line 23
def test_to_key
  assert model.respond_to?(:to_key), "The model should respond to to_key"
  def model.persisted?() false end
  assert model.to_key.nil?, "to_key should return nil when `persisted?` returns false"

Responds to to_param

Returns a string representing the object’s key suitable for use in URLs or nil if model.persisted? is false.

Implementers can decide to either raise an exception or provide a default in case the record uses a composite primary key. There are no tests for this behavior in lint because it doesn’t make sense to force any of the possible implementation strategies on the implementer. However, if the resource is not persisted?, then to_param should always return nil.

# File activemodel/lib/active_model/lint.rb, line 39
def test_to_param
  assert model.respond_to?(:to_param), "The model should respond to to_param"
  def model.to_key() [1] end
  def model.persisted?() false end
  assert model.to_param.nil?, "to_param should return nil when `persisted?` returns false"

Responds to valid?

Returns a boolean that specifies whether the object is in a valid or invalid state.

# File activemodel/lib/active_model/lint.rb, line 50
def test_valid?
  assert model.respond_to?(:valid?), "The model should respond to valid?"
  assert_boolean model.valid?, "valid?"