An example way to verify that a foreigner key is created for your model

sample_foreigner_usage_spec.rb

context "foreign keys" do
  def foreign_key_definition_to(to_table, options={})
    defaults = { :primary_key => "id", :column => "#{to_table.singularize}_id" }
    defaults[:name] = "#{subject.class.table_name}_#{defaults[:column]}_fk"
    options = defaults.merge(options)
    Foreigner::ConnectionAdapters::ForeignKeyDefinition.new(subject.class.table_name, to_table, options)
  end

  it "should include some_model_records with dependent delete" do
    subject.connection.foreign_keys(subject.class.table_name).should include(foreign_key_definition_to("some_model_records", { :dependent => :delete }))
  end
end