1 files changed, 157 insertions, 0 deletions
diff --git a/spec/rubocop/cop/gitlab/module_with_instance_variables_spec.rb b/spec/rubocop/cop/gitlab/module_with_instance_variables_spec.rb
new file mode 100644
index 00000000000..1fd40653f79
--- /dev/null
+++ b/spec/rubocop/cop/gitlab/module_with_instance_variables_spec.rb
@@ -0,0 +1,157 @@
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/gitlab/module_with_instance_variables'
+
+describe RuboCop::Cop::Gitlab::ModuleWithInstanceVariables do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  shared_examples('registering offense') do |options|
+    let(:offending_lines) { options[:offending_lines] }
+
+    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
+
+  shared_examples('not registering offense') do
+    it 'does not register offenses' do
+      inspect_source(cop, source)
+
+      expect(cop.offenses).to be_empty
+    end
+  end
+
+  context 'when source is a regular module' do
+    it_behaves_like 'registering offense', offending_lines: [3] do
+      let(:source) do
+        <<~RUBY
+          module M
+            def f
+              @f = true
+            end
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when source is a nested module' do
+    it_behaves_like 'registering offense', offending_lines: [4] do
+      let(:source) do
+        <<~RUBY
+          module N
+            module M
+              def f
+                @f = true
+              end
+            end
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when source is a nested module with multiple offenses' do
+    it_behaves_like 'registering offense', offending_lines: [4, 12] 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
+    end
+  end
+
+  context 'when source is using simple or ivar assignment' do
+    it_behaves_like 'not registering offense' do
+      let(:source) do
+        <<~RUBY
+          module M
+            def f
+              @f ||= true
+            end
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when source is using simple ivar' do
+    it_behaves_like 'not registering offense' do
+      let(:source) do
+        <<~RUBY
+          module M
+            def f?
+              @f
+            end
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when source is defining initialize' do
+    it_behaves_like 'not registering offense' do
+      let(:source) do
+        <<~RUBY
+          module M
+            def initialize
+              @a = 1
+              @b = 2
+            end
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when source is using simple or ivar assignment with other ivar' do
+    it_behaves_like 'registering offense', offending_lines: [3] do
+      let(:source) do
+        <<~RUBY
+          module M
+            def f
+              @f ||= g(@g)
+            end
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when source is using or ivar assignment with something else' do
+    it_behaves_like 'registering offense', offending_lines: [3, 4] do
+      let(:source) do
+        <<~RUBY
+          module M
+            def f
+              @f ||= true
+              @f.to_s
+            end
+          end
+        RUBY
+      end
+    end
+  end
+end