module ThoughtBot::Shoulda::ActiveRecord::Assertions

assert_bad_value(Product, :price, "0")
@product = Product.new(:tangible => true)

assert_bad_value(User, :email, "invalid")

instead.
the same name as the class (underscored), that object will be used
instantiated before the assertion. If an instance variable exists with
If a class is passed as the first argument, a new object will be

assert_bad_value(User.new, :ssn, "123", /length/)
assert_bad_value(User.new, :email, "invalid")

contained within the list of errors for that attribute.
value by making sure the error_message_to_expect is
Asserts that an Active Record model invalidates the passed

def assert_bad_value(object_or_klass, attribute, value,
                     error_message_to_expect = DEFAULT_ERROR_MESSAGES[:invalid])
  object = get_instance_of(object_or_klass)
  object.send("#{attribute}=", value)
  assert !object.valid?, "#{object.class} allowed #{value.inspect} as a value for #{attribute}"
  assert object.errors.on(attribute), "There are no errors on #{attribute} after being set to #{value.inspect}"
  assert_contains(object.errors.on(attribute), error_message_to_expect, "when set to #{value.inspect}")
end