Rspec：如何使通过测试失败？

Question

I have a client object in a ruby gem that needs to work with a web service. I am testing to verify that it can be properly initialised and throws an error if all arguments are not passed in.

Here are my specs:

describe 'Contentstack::Client Configuration' do
  describe ":access_token" do
    it "is required" do
      expect { create_client(access_token: nil) }.to raise_error(ArgumentError)
    end
  end

  describe ":access_key" do
    it "is required" do
      expect { create_client(access_key: nil) }.to  raise_error(ArgumentError)
    end
  end

  describe ":environment" do
    it "is required" do
      expect { create_client(environment: nil) }.to  raise_error(ArgumentError)
    end
  end
end

Here is the gem code:

module Contentstack

  class Client
    attr_reader :access_key, :access_token, :environment

    def initialize(access_key:, access_token:, environment:)
      @access_key = access_key
      @access_token = access_token
      @environment = environment

      validate_configuration!
    end

    def validate_configuration!
      fail(ArgumentError, "You must specify an access_key")  if access_key.nil?
      fail(ArgumentError, "You must specify an access_token")  if access_token.nil?
      fail(ArgumentError, "You must specify an environment")  if environment.nil?
    end
  end

end

and here is the spec_helper method:

def create_client(access_token:, access_key:, environment:)
  Contentstack::Client.new(access_token: access_token, access_key: access_key, environment: environment)
end

The problem is: I can't find a way to make these tests fail before they pass. These tests always pass because ruby throws an ArgumentError by default. I don't understand if this is the right approach to TDD. How do I get into a red-green-refactor cycle with this scenario?

Answer 1

create_client raises the ArgumentError , because it expects three keyword arguments and you are passing only one: (maybe you should have tested your helper, too)

def create_client(access_token:, access_key:, environment:)
  # intentionally left empty
end

create_client(access_key: nil)
# in `create_client': missing keywords: access_token, environment (ArgumentError)

You could use default values in your helper to overcome this:

def create_client(access_token: :foo, access_key: :bar, environment: :baz)
  Contentstack::Client.new(access_token: access_token, access_key: access_key, environment: environment)
end

create_client(access_key: nil)
# in `validate_configuration!': You must specify an access_key (ArgumentError)

Finally, you could be more specific regarding the error message:

expect { ... }.to raise_error(ArgumentError, 'You must specify an access_key')

Answer 2

please refer to the answer by Stefan, it's way more proper

The proper way would be to mock Client#validate_configuration! to do nothing, but here it might be even simpler. Put in your test_helper.rb :

Client.prepend(Module.new do
  def validate_configuration!; end
end)

Frankly, I do not see any reason to force tests to fail before they pass in this particular case. To follow the TDD, you should have been running tests before validate_configuration! implementation. Then those tests would have failed.

But since you have implemented it in advance, there is no need to blindly thoughtless follow the rule “test must fail before pass.”