module ActiveModel::Serializer::Lint::Tests

def assert_instance_of(result, name) 

def assert_instance_of(result, name)
  assert result.instance_of?(name), "#{result} should be an instance of #{name}"
end

def resource 

def resource
  @resource or fail "'@resource' must be set as the linted object"
end

def test_active_model_errors 

def test_active_model_errors
  assert_respond_to resource, :errors
end

def test_active_model_errors_human_attribute_name 

def test_active_model_errors_human_attribute_name
  assert_respond_to resource.class, :human_attribute_name
  assert_equal(-2, resource.class.method(:human_attribute_name).arity)
end

def test_active_model_errors_lookup_ancestors 

def test_active_model_errors_lookup_ancestors
  assert_respond_to resource.class, :lookup_ancestors
  assert_equal 0, resource.class.method(:lookup_ancestors).arity
end

def test_as_json

or by the JSON gem when required.
which includes ActiveModel::Serializers::JSON.
Typically, it is implemented either by including ActiveModel::Serialization
It may delegate to serializable_hash
as_json returns a hash representation of a serialized object.

Fails otherwise.
zero or one arguments.
Passes if the object responds to as_json and if it takes 
def test_as_json
  assert_respond_to resource, :as_json
  resource.as_json
  resource.as_json(nil)
end

def test_cache_key

adapter. It is not required unless caching is enabled.
and is part of the (self-expiring) cache_key, which is used by the
cache_key returns a (self-expiring) unique key for the object,

Fails otherwise.
Passes if the object responds to cache_key 
def test_cache_key
  assert_respond_to resource, :cache_key
  actual_arity = resource.method(:cache_key).arity
  assert_includes [-1, 0], actual_arity, "expected #{actual_arity.inspect} to be 0 or -1"
end

def test_id

It is not required unless caching is enabled.
id returns a unique identifier for the object.

Fails otherwise.
arguments.
Passes if the object responds to id and if it takes no 
def test_id
  assert_respond_to resource, :id
  assert_equal 0, resource.method(:id).arity
end

def test_model_name

It is not required unless caching is enabled.
It is used by the serializer to identify the object's type.
model_name returns an ActiveModel::Name instance.

Fails otherwise.
is in an instance of +ActiveModel::Name+.
Passes if the object's class responds to model_name and if it 
def test_model_name
  resource_class = resource.class
  assert_respond_to resource_class, :model_name
  assert_instance_of resource_class.model_name, ActiveModel::Name
end

def test_read_attribute_for_serialization

Typically, it is implemented by including ActiveModel::Serialization.
read_attribute_for_serialization gets the attribute value for serialization

Fails otherwise.
and if it requires one argument (the attribute to be read).
Passes if the object responds to read_attribute_for_serialization 
def test_read_attribute_for_serialization
  assert_respond_to resource, :read_attribute_for_serialization, 'The resource should respond to read_attribute_for_serialization'
  actual_arity = resource.method(:read_attribute_for_serialization).arity
  # using absolute value since arity is:
  #  1 for def read_attribute_for_serialization(name); end
  # -1 for alias :read_attribute_for_serialization :send
  assert_equal 1, actual_arity.abs, "expected #{actual_arity.inspect}.abs to be 1 or -1"
end

def test_serializable_hash

Typically, it is implemented by including ActiveModel::Serialization.
serializable_hash returns a hash representation of a object's attributes.

Fails otherwise.
zero or one arguments.
Passes if the object responds to serializable_hash and if it takes 
def test_serializable_hash
  assert_respond_to resource, :serializable_hash, 'The resource should respond to serializable_hash'
  resource.serializable_hash
  resource.serializable_hash(nil)
end

def test_to_json

Typically, it is implemented on all objects when the JSON gem is required.
It may be called on the result of as_json.
to_json returns a string representation (JSON) of a serialized object.

Fails otherwise.
zero or one arguments.
Passes if the object responds to to_json and if it takes 
def test_to_json
  assert_respond_to resource, :to_json
  resource.to_json
  resource.to_json(nil)
end

def test_updated_at

It is not required unless caching is enabled.
is part of the (self-expiring) cache_key, which is used by the adapter.
updated_at returns a Time object or iso8601 string and

Fails otherwise.
arguments.
Passes if the object responds to updated_at and if it takes no 
def test_updated_at
  assert_respond_to resource, :updated_at
  actual_arity = resource.method(:updated_at).arity
  assert_equal 0, actual_arity
end