1 files changed, 158 insertions, 0 deletions
diff --git a/spec/lib/gitlab/utils/override_spec.rb b/spec/lib/gitlab/utils/override_spec.rb
new file mode 100644
index 00000000000..7c97cee982a
--- /dev/null
+++ b/spec/lib/gitlab/utils/override_spec.rb
@@ -0,0 +1,158 @@
+require 'spec_helper'
+
+describe Gitlab::Utils::Override do
+  let(:base) { Struct.new(:good) }
+
+  let(:derived) { Class.new(base).tap { |m| m.extend described_class } }
+  let(:extension) { Module.new.tap { |m| m.extend described_class } }
+
+  let(:prepending_class) { base.tap { |m| m.prepend extension } }
+  let(:including_class) { base.tap { |m| m.include extension } }
+
+  let(:klass) { subject }
+
+  def good(mod)
+    mod.module_eval do
+      override :good
+      def good
+        super.succ
+      end
+    end
+
+    mod
+  end
+
+  def bad(mod)
+    mod.module_eval do
+      override :bad
+      def bad
+        true
+      end
+    end
+
+    mod
+  end
+
+  shared_examples 'checking as intended' do
+    it 'checks ok for overriding method' do
+      good(subject)
+      result = klass.new(0).good
+
+      expect(result).to eq(1)
+      described_class.verify!
+    end
+
+    it 'raises NotImplementedError when it is not overriding anything' do
+      expect do
+        bad(subject)
+        klass.new(0).bad
+        described_class.verify!
+      end.to raise_error(NotImplementedError)
+    end
+  end
+
+  shared_examples 'nothing happened' do
+    it 'does not complain when it is overriding something' do
+      good(subject)
+      result = klass.new(0).good
+
+      expect(result).to eq(1)
+      described_class.verify!
+    end
+
+    it 'does not complain when it is not overriding anything' do
+      bad(subject)
+      result = klass.new(0).bad
+
+      expect(result).to eq(true)
+      described_class.verify!
+    end
+  end
+
+  before do
+    # Make sure we're not touching the internal cache
+    allow(described_class).to receive(:extensions).and_return({})
+  end
+
+  describe '#override' do
+    context 'when STATIC_VERIFICATION is set' do
+      before do
+        stub_env('STATIC_VERIFICATION', 'true')
+      end
+
+      context 'when subject is a class' do
+        subject { derived }
+
+        it_behaves_like 'checking as intended'
+      end
+
+      context 'when subject is a module, and class is prepending it' do
+        subject { extension }
+        let(:klass) { prepending_class }
+
+        it_behaves_like 'checking as intended'
+      end
+
+      context 'when subject is a module, and class is including it' do
+        subject { extension }
+        let(:klass) { including_class }
+
+        it 'raises NotImplementedError because it is not overriding it' do
+          expect do
+            good(subject)
+            klass.new(0).good
+            described_class.verify!
+          end.to raise_error(NotImplementedError)
+        end
+
+        it 'raises NotImplementedError when it is not overriding anything' do
+          expect do
+            bad(subject)
+            klass.new(0).bad
+            described_class.verify!
+          end.to raise_error(NotImplementedError)
+        end
+      end
+    end
+  end
+
+  context 'when STATIC_VERIFICATION is not set' do
+    before do
+      stub_env('STATIC_VERIFICATION', nil)
+    end
+
+    context 'when subject is a class' do
+      subject { derived }
+
+      it_behaves_like 'nothing happened'
+    end
+
+    context 'when subject is a module, and class is prepending it' do
+      subject { extension }
+      let(:klass) { prepending_class }
+
+      it_behaves_like 'nothing happened'
+    end
+
+    context 'when subject is a module, and class is including it' do
+      subject { extension }
+      let(:klass) { including_class }
+
+      it 'does not complain when it is overriding something' do
+        good(subject)
+        result = klass.new(0).good
+
+        expect(result).to eq(0)
+        described_class.verify!
+      end
+
+      it 'does not complain when it is not overriding anything' do
+        bad(subject)
+        result = klass.new(0).bad
+
+        expect(result).to eq(true)
+        described_class.verify!
+      end
+    end
+  end
+end