RSpectre

rspectre is a tool to remove the dead and errant code haunting your test suite.

Static analysis tools like rubocop-rspec, while very helpful in their own right, generally cannot detect most unused or misused test setup (especially when it spans multiple files) or are forced to have high false positive rates.

rspectre works a bit differently. By probing your test suite as it runs, rspectre can reliably detect and remove a number of common mistakes with virtually no false positives, including:

• Unused let statements
• Unused subject statements
• Unused shared_context and shared_examples statements

RSpec.describe 'example' do
  subject { 'i get overridden later' }

  let(:foo) { 'an unused foo' }

  shared_examples 'unused example' do
    it 'is useless since it is not included' do
      expect(2 + 2).to eql(5)
    end
  end

  shared_examples 'used' do
    let(:bar) { 'an unused bar' }

    it 'asserts something' do
      expect(subject).to eql(baz)
    end
  end

  context 'some context' do
    subject { 'x' }

    let(:baz) { 'x' }

    include_examples 'used'
  end
end

To install rspectre, run:

$ gem install rspectre

or add

gem 'rspectre'

to your Gemfile.

Simply running

$ rspectre

will invoke your rspec test suite and check for various offenses. It runs rspec with rspec --fail-fast spec by default. If you need to pass custom arguments to rspec, you can use the --rspec flag and pass a quoted string of rspec arguments, as shown below:

$ rspectre --rspec '--some-rspec-flag tests'

If you want to automatically delete dead code that rspectre finds, simply use the --auto-correct flag.

$ rspectre --auto-correct

Note: --auto-correct is unpolished and may leave behind awkward whitespace or otherwise misbehave. YMMV.

You should generally run your entire test suite with rspectre. rspectre inserts probes in all of your specs and helpers as they are require'd and then waits to observe them being used. If, for example, your spec helper requires all your shared examples but you only run a subset of your tests (which don't happen to use all of the aforementioned shared examples), it may appear to rspectre like some of those shared examples are unused when they are not. If you do not run your whole test suite, you'll likely have to sift through some false positives.

My intent is to support all non-EOL ruby versions and the last 4 minor versions of rspec. At the time of writing (2024-11-28), those are (3.1, 3.2, 3.3, 3.4) and (3.10, 3.11, 3.12, and 3.13, respectively). If you encounter an issue on a different version of rspec, please try upgrading first. If you still have a problem, please file an issue.

Please try out rspectre on your codebase--I'd love general feedback and, especially, bug reports. If you find something weird or --auto-correct eats your dog along with your homework, open an issue!

Also, if you have an idea for something you think rspectre might be able to reasonably detect, feel free to propose it in an issue as well.