What exception is raised when using + on symbols in Ruby?

Doing the Ruby Koans, in the file about_symbols at line 88, I'm not sure of the answer.

This is the code:

def test_symbols_cannot_be_concatenated
    # Exceptions will be pondered further farther down the path
    assert开发者_开发问答_raise(what should i put?) do
      :cats + :dogs
    end

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The point of the Ruby Koans is to learn by reading and trying things out.

Open up a terminal and start irb. Then try using the + operator on two symbols. Check the error you get and substitute it as appropriate in the Koans file.

Assuming that your prompt ends in $, that will look something like this:

$ irb
irb(main):001:0> :cats + :dogs

The answer you need will be clear pretty quickly in the error that irb spits out.

---

To go through step by step in case your completely new to Ruby you could try:

1. Open up a terminal
2. Type irb at your prompt to get to the interactive ruby prompt
   • This is where you can quickly try out different Ruby things
3. Type the command in question :cats + :dogs
4. Review the output which will look like

NoMethodError: undefined method `+' for :cats:Symbol
  from (irb):1

The name of the exception thrown which is what you are looking for is the first thing e.g. NoMethodError