Rspec matcher to test if a class initialize valid instances.

initialize_as_a_valid_instance_matcher.rb

# test if ActiveRecord classes (or ActiveModel) initialize valid instances
# it { should initialize_as_a_valid_instance }

RSpec::Matchers.define :initialize_as_a_valid_instance do

  match do |actual|
    actual.valid?
  end

  description do
    "initialize as a valid #{actual.class.to_s} instance"
  end

  failure_message_for_should do |text|
    "expected object to initialize as a valid instance but it has errors: " +
      actual.errors.full_messages.join(", ")
  end

end