Why does ruby return `true` for a method call?
So this is a short tutorial I found at Rspec: w3ii.com: rspec about this explanation about rspec helpers. This is the code for the example:
class Dog
attr_reader :good_dog, :has_been_walked
def initialize(good_or_not)
@good_dog = good_or_not
@has_been_walked = false
end
def walk_dog
@has_been_walked = true
end
end
describe Dog do
def create_and_walk_dog(good_or_bad)
Dog.new(good_or_bad).walk_dog
end
it 'should be able to create and walk a good dog' do
dog = create_and_walk_dog(true)
expect(dog.good_dog).to be true
expect(dog.has_been_walked).to be true
end
end
When I run this I get this error:
NoMethodError: undefined method 'good_dog' for true: TrueClass
#. / Dor.rb: 22: in 'block <2 levels> in>'
I can't figure out how the call to Dog.new () returns true: a TrueClass object instead of a simple dog.
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Which, since it create_and_walk_dog
returns, what the method walk_dog
returns
To return a dog from a method create_and_walk_dog
, you need something like
describe Dog do
def create_and_walk_dog(good_or_bad)
dog = Dog.new(good_or_bad)
dog.walk_dog
dog
end
it 'should be able to create and walk a good dog' do
dog = create_and_walk_dog(true)
expect(dog.good_dog).to be true
expect(dog.has_been_walked).to be true
end
end
Or continue with the wait block:
describe Dog do
it 'should be able to create and walk a good dog' do
dog = Dog.new(true)
expect(dog.good_dog).to be true
expect {
dog.walk_dog
}.to change(dog, :has_been_walked).from(false).to true
end
end
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I think for clarity, you could / should have used the RSpec let method here is not the complete method definition included in your RSpec file.If your _walk_dog_ method returns itself as suggested in another answer, I see that your current one is fixed here RSpec implementation, but doesn't help you anywhere in your potential application. A hypothetical case where bad dogs return false for _dog.walk_dog_ randomly 50% of the time, or just don't cooperate at all.
class Dog
attr_reader :good_dog, :has_been_walked
def initialize(good_or_not)
@good_dog = good_or_not
@has_been_walked = false
end
# Command to attempt walking a dog.
#
# @api public
#
# @example
# good_dog = Dog.new(true)
# good_dog.walk_dog # => Will always return true for good dogs.
# bad_dog = Dog.new(false)
# bad_dog.wal_dog # => 50/50 chance of true or false
def walk_dog
return @has_been_walked = true if @good_dog
[true, false].sample
end
end
describe Dog do
let(:good_dog) { Dog.new(true) }
it 'should always be able to walk a good dog' do
expect(good_dog.walk_dog).to be true
end
it 'should track if the dog has been walked' do
expect {
good_dog.walk_dog
}.to change(dog, :has_been_walked).from(false).to true
end
end
Forward for discussion as well, but you only have to assert one thing per spec, unless you hit the db or do something for a relatively long time.
PS They are all good dogs Brent
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