diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 3ae98ce..f51e757 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -21,6 +21,12 @@ jobs:
     - name: Setup Graphviz
       uses: ts-graphviz/setup-graphviz@v1
     - uses: actions/checkout@v3
+    - name: Generate lockfile from gemspec
+      run: bundle lock --add-platform x86_64-linux
+    - name: Install dependencies
+      run: bundle install --jobs 4 --retry 3
+    - name: Check RuboCop version
+      run: bundle exec rubocop -V
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:
diff --git a/.gitignore b/.gitignore
index b04a8c8..2cc7067 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,3 +9,6 @@
 
 # rspec failure tracking
 .rspec_status
+
+Gemfile.lock
+.ruby-version
\ No newline at end of file
diff --git a/Rakefile b/Rakefile
index 336115d..d1bd74f 100644
--- a/Rakefile
+++ b/Rakefile
@@ -11,4 +11,4 @@ require "rubocop/rake_task"
 
 RuboCop::RakeTask.new
 
-task default: %i[spec rubocop steep:check]
+task default: %i[steep:check spec rubocop]
diff --git a/lib/snapbot/rspec/lets.rb b/lib/snapbot/rspec/lets.rb
index 8543846..acb2d57 100644
--- a/lib/snapbot/rspec/lets.rb
+++ b/lib/snapbot/rspec/lets.rb
@@ -16,7 +16,7 @@ def collect
 
       def _collect(klass, lets)
         lets.tap do
-          next if klass.to_s == "RSpec::ExampleGroups"
+          next if klass.to_s == "RSpec::ExampleGroups" # stop when we hit the top
 
           lets.concat(klass::LetDefinitions.instance_methods(false))
           parent_class = klass.to_s.deconstantize.constantize
diff --git a/snapbot.gemspec b/snapbot.gemspec
index 2a1447d..9b3c4ad 100644
--- a/snapbot.gemspec
+++ b/snapbot.gemspec
@@ -37,6 +37,7 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "launchy"
   spec.add_development_dependency "rbs"
+  spec.add_development_dependency "rubocop", "~> 1.21"
   spec.add_development_dependency "sqlite3"
   spec.add_development_dependency "steep"
 
diff --git a/spec/snapbot/rspec/lets_spec.rb b/spec/snapbot/rspec/lets_spec.rb
new file mode 100644
index 0000000..33d9ebb
--- /dev/null
+++ b/spec/snapbot/rspec/lets_spec.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+RSpec.describe Snapbot::RSpec::Lets do
+  describe "#collect" do
+    subject { described_class.new(self).collect }
+
+    context "when there are lets" do
+      let(:foo) { "bar" }
+      let(:bar) { "baz" }
+
+      it { is_expected.to match_array %i[foo bar subject] }
+    end
+  end
+
+  describe "#collect when there are no lets" do # (cannot use a `subject`, separate describe)
+    it "returns an empty array" do
+      expect(described_class.new(self).collect).to be_empty
+    end
+  end
+end