Add cop to make sure we don't use ivar in a module

1 files changed, 117 insertions, 0 deletions

diff --git a/spec/rubocop/cop/module_with_instance_variables_spec.rb b/spec/rubocop/cop/module_with_instance_variables_spec.rb
new file mode 100644
index 00000000000..ce2e156e423
--- /dev/null
+++ b/spec/rubocop/cop/module_with_instance_variables_spec.rb
@@ -0,0 +1,117 @@
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../rubocop/cop/module_with_instance_variables'
+
+describe RuboCop::Cop::ModuleWithInstanceVariables do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  shared_examples('registering offense') do
+    it 'registers an offense when instance variable is used in a module' do
+      inspect_source(cop, source)
+
+      aggregate_failures do
+        expect(cop.offenses.size).to eq(offending_lines.size)
+        expect(cop.offenses.map(&:line)).to eq(offending_lines)
+      end
+    end
+  end
+
+  context 'when source is a regular module' do
+    let(:source) do
+      <<~RUBY
+        module M
+          def f
+            @f ||= true
+          end
+        end
+      RUBY
+    end
+
+    let(:offending_lines) { [3] }
+
+    it_behaves_like 'registering offense'
+  end
+
+  context 'when source is a nested module' do
+    let(:source) do
+      <<~RUBY
+        module N
+          module M
+            def f
+              @f = true
+            end
+          end
+        end
+      RUBY
+    end
+
+    let(:offending_lines) { [4] }
+
+    it_behaves_like 'registering offense'
+  end
+
+  context 'when source is a nested module with multiple offenses' do
+    let(:source) do
+      <<~RUBY
+        module N
+          module M
+            def f
+              @f ||= true
+            end
+
+            def g
+              true
+            end
+
+            def h
+              @h = true
+            end
+          end
+        end
+      RUBY
+    end
+
+    let(:offending_lines) { [4, 12] }
+
+    it_behaves_like 'registering offense'
+  end
+
+  context 'when source is offending but it is a rails helper' do
+    before do
+      allow(cop).to receive(:rails_helper?).and_return(true)
+    end
+
+    it 'does not register offenses' do
+      inspect_source(cop, <<~RUBY)
+        module M
+          def f
+            @f ||= true
+          end
+        end
+      RUBY
+
+      expect(cop.offenses).to be_empty
+    end
+  end
+
+  context 'when source is offending but it is a rails mailer' do
+    before do
+      allow(cop).to receive(:rails_mailer?).and_return(true)
+    end
+
+    it 'does not register offenses' do
+      inspect_source(cop, <<~RUBY)
+        module M
+          def f
+            @f = true
+          end
+        end
+      RUBY
+
+      expect(cop.offenses).to be_empty
+    end
+  end
+end