RSpec.describe TTY::Spinner::Multi, "#on" do
  let(:output) { StringIO.new("", "w+") }

  it "fails to register a callback with invalid event name" do
    spinners = TTY::Spinner::Multi.new(output: output)

    expect {
      spinners.on(:unknown_event) { :noop }
    }.to raise_error(ArgumentError, /The event unknown_event does not exist/)
  end
end