Failures:

  1) Zoo#add_animal should raise an error if there are no empty cages
     Failure/Error: expect { zoo.add_animal(python) }.to raise_error(ZooAtCapacity)

     NameError:
       uninitialized constant ZooAtCapacity
     # ./spec/7_zoo_spec.rb:70:in `block (3 levels) in <top (required)>'

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32 examples, 1 failure

Failed examples:

rspec ./spec/7_zoo_spec.rb:63 # Zoo#add_animal should raise an error if there are no empty cages