RuboCop RSpec Autocorrect Bug: ScatteredSetup Cop
The Problem with Scattered Setup in RSpec Specs
We've stumbled upon a rather tricky issue when using RuboCop RSpec, specifically with its RSpec/ScatteredSetup cop. This cop is designed to help keep your RSpec test setup clean and organized by flagging multiple before, after, or around hooks within the same example group. The intention is great: a single before block generally makes it easier to understand the setup logic for your tests. However, we’ve found a scenario where the autocorrect functionality of this cop can actually break your specs, leading to unexpected failures. This happens when you define a helper class method that itself contains a before block. RuboCop's autocorrect, in its attempt to consolidate before hooks, incorrectly pulls the content from this helper method into the main before block, effectively merging setups that were intended to be distinct or ordered.
Let's dive into a practical example to illustrate this. Imagine you have a Gemfile that includes rspec, rubocop, and rubocop-rspec. You also have a basic .rubocop.yml configuration that simply loads the rubocop-rspec gem. The core of the problem lies within a spec file, let's call it scattered_spec.rb. In this file, we define a simple class Foo with a test_method. The spec itself starts with a before block that uses allow(Foo).to receive(:test_method).and_return('initial_before'). This sets up a baseline expectation for Foo.test_method. Then, we define a helper class method, self.extra_setup. Inside this method, we have another before block: before { allow(Foo).to receive(:test_method).and_return('overwritten_before') }. The intention here is to override the initial setup within a specific context. We then have two contexts: one that uses the initial setup and another that calls extra_setup before its tests. The first context correctly expects 'initial_before', while the second expects 'overwritten_before', demonstrating a clear intent of sequential or context-specific setup logic. This structure, while functional, triggers the RSpec/ScatteredSetup cop when RuboCop's autocorrect is applied, leading to the unexpected behavior we're discussing.
How Autocorrect Goes Awry
When RuboCop's RSpec/ScatteredSetup cop encounters the code structure we just outlined, it identifies two before blocks within what it perceives as the same scope. The cop's logic is generally sound: having multiple before hooks directly in an RSpec.describe block can indeed make the test setup harder to follow. However, it fails to recognize that one of these before hooks is encapsulated within a helper class method (extra_setup). The cop's autocorrect feature then proceeds to extract the content of the before block found inside extra_setup and appends it to the primary before block defined directly within the RSpec.describe block. Simultaneously, it attempts to
