Adding an error doesn't mark the outcome as invalid

[tfausak]

class Interaction < ActiveInteraction::Base
  boolean :b
  def execute; errors.add(:b) end
end
p Interaction.run(b: true).valid?
# => true

[tfausak]

You shouldn't modify errors from within the execute method. Instead, define custom validators:

class Interaction < ActiveInteraction::Base
  boolean :b
  validate :v
  def v; errors.add(:b) end
  def execute; b end
end
p Interaction.run(b: true).valid?
# => false

The expected behavior for valid? is to clear custom errors. Check out this Stack Overflow question or the ActiveModel::Validations documentation. The documentation has the source for valid?, which includes:

errors.clear