Question

I have a rspec test to validate a function which works depending on the rails version. So in my code I’m planning to use Rails::VERSION::String to get the rails version.

Before the test I tried to explicitly set the rails version like this

Rails::VERSION = "2.x.x"

But when I run the test seems like rspec cannot find the Rails variable and gives me the error

uninitialized constant Rails (NameError)

So what might be I’m missing here, thanks in advance

Answer 1

The best way to do this is to encapsulate the rails version check in code that you control, and then stub out the different test values you want to exercise.

For example:

module MyClass
  def self.rails_compatibility
    Rails.version == '2.3' ? 'old_way' : 'new_way'
  end
end

describe OtherClass do
  context 'with old_way' do
    before { MyClass.stubs(:rails_compatibility => 'old_way') }
    it 'should do this' do
      # expectations...
    end
  end

  context 'with new_way' do
    before { MyClass.stubs(:rails_compatibility => 'new_way') }
    it 'should do this' do
      # expectations...
    end
  end
end

Alternately, if your versioning logic is that complex, you should stub out a simple wrapper:

module MyClass
  def self.rails_version
    ENV['RAILS_VERSION']
  end

  def self.behavior_mode
    rails_version == '2.3' ? 'old_way' : 'new_way'
  end
end

describe MyClass do
  context 'Rails 2.3' do
    before { MyClass.stubs(:rails_version => '2.3') }
    it 'should use the old way' do
      MyClass.behavior_mode.should == 'old_way'
    end
  end

  context 'Rails 3.1' do
    before { MyClass.stubs(:rails_version => '3.1') }
    it 'should use the new way' do
      MyClass.behavior_mode.should == 'new_way'
    end
  end
end