Kerry Buckley

What’s the simplest thing that could possibly go wrong?

Archive for March, 2013

FESuffolk Jasmine lightning talk

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At last night’s FESuffolk meeting I gave a lightning talk on getting started with unit-testing Javascript/coffeescript using jasmine-headless-webkit. I made a screen recording, so if you missed it you can still experience my frantic babbling (I had Keynote set to auto-advance, using the Ignite 20 × 15 second slide format, and as usual I tried to cram too much into each slide).

If you don’t want to watch the recording, you can look at the slides and guess what I might have been saying, read the example code (the commits try to build up in small steps), or just play with the utterly pointless app that the example implements.

Written by Kerry

March 26th, 2013 at 8:00 pm

Interesting little rSpec gotcha

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This one had Adam and me stumped for a while. Trying to check that a method is only called on objects that respond to it:

describe "Foo#call_all_the_things" do
  let(:foo_1) { stub :foo_1, bar: "hello" }
  let(:foo_2) { stub :foo_2 }
  subject { Foo.new foo_1, foo_2 }

  it "only calls bar on objects that respond to it" do
    foo_1.should_receive :bar
    foo_2.should_not_receive :bar
    subject.call_all_the_things(:bar)
  end
end

class Foo
  def initialize *things
    @things = things
  end

  def call_all_the_things method
    @things.each do |thing|
      thing.send method if thing.respond_to? method
    end
  end
end


  1) Foo#call_all_the_things only calls bar on objects that respond to it
     Failure/Error: thing.send method if thing.respond_to? method
       (Stub :foo_2).bar(no args)
           expected: 0 times
           received: 1 time

Hmm. Why is it calling bar on the thing that doesn’t respond to it? Perhaps rSpec doubles don’t handle respond_to? properly?

[1] pry(main)> require "rspec/mocks/standalone"
=> true
[2] pry(main)> foo = stub foo: 123
=> #<RSpec::Mocks::Mock:0x3fd07d246f34 @name=nil>
[3] pry(main)> foo.respond_to? :foo
=> true
[4] pry(main)> foo.respond_to? :bar
=> false

Nope.

FX: lightbulb above head

Of course! To do the should_not_receive check, it needs to stub the method, which means it responds to it!

Two possible solutions: either let the fact that the missing method isn’t called be tested implicitly, or specify that when objects that don’t respond to the method exist, no NoMethodError is raised.

Written by Kerry

March 20th, 2013 at 3:04 pm

Posted in rspec,Ruby,Software