module ActiveModel::Serializer::Lint::Tests

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