How can I clear class variables between rspec tests in ruby

Question

I have the following class: I want to ensure the class url is only set once for all instances.

class DataFactory
  @@url = nil

  def initialize()
begin
    if @@url.nil?
       Rails.logger.debug "Setting url"
       @@url = MY_CONFIG["my value"]
    end
rescue Exception
  raise DataFactoryError, "Error!"
end
  end
end

I have two tests:

it "should log a message" do
  APP_CONFIG = {"my value" => "test"}
  Rails.stub(:logger).and_return(logger_mock)
  logger_mock.should_receive(:debug).with "Setting url"

  t = DataFactory.new
  t = nil
end

it "should throw an exception" do
  APP_CONFIG = nil

  expect {
    DataFactory.new
  }.to raise_error(DataFactoryError, /Error!/)
end

The problem is the second test never throws an exception as the @@url class variable is still set from the first test when the second test runs. Even though I have se the instance to nil at the end of the first test garbage collection has not cleared the memory before the second test runs:

Any ideas would be great! I did hear you could possibly use Class.new but I am not sure how to go about this.

Not exactly related to your problem, but: never use @@class variables in Ruby. Use @class instance variables instead. They behave far more predictably. — Marnen Laibow-Koser
– Marnen Laibow-Koser, Commented Nov 28, 2011 at 19:45

Mori · Accepted Answer · 2011-11-25 23:17:44Z

27

describe DataFactory
  before(:each) { DataFactory.class_variable_set :@@url, nil }
  ...
end

edited Nov 25, 2011 at 23:17

answered Nov 25, 2011 at 22:56

Mori

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1 Comment

Kevin White Over a year ago

When I ran this I got the following error: NameError: uninitialized class variable @@url in Object I got it to work using: before(:each) do DataFactory.class_eval {class_variable_set :@@url, nil} end I am using JRuby 1.6.5 which I believe uses Ruby 1.8.9 and class_variable_set might be private in this version so I had to use class_eval See: [khelll.com/blog/ruby/ruby-reflection-2/]

jleverenz · Accepted Answer · 2014-03-13 04:12:50Z

8

Here is an alternative to the accepted answer, which while wouldn't solve your particular example, I'm hoping it might help a few people with a question in the same vein. If the class in question doesn't specify a default value, and remains undefined until set, this seems to work:

describe DataFactory
  before(:each) do
    DataFactory.remove_class_variable :@@url if DataFactory.class_variable_defined? :@@url
  end
  ...
end

Works for me with a class with something more like:

def initialize
  @@url ||= MY_CONFIG["my value"]
  ...
end

answered Mar 13, 2014 at 4:12

jleverenz

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1 Comment

weston Over a year ago

and similarly with class instance variable: described_class.remove_instance_variable(:@foo) if described_class.instance_variable_defined?(:@foo)

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