Add missing ExclusiveLeaseGuard spec

This tests the #try_obtain_lease
method of the ExclusiveLeaseGuard class

spec/services/concerns/exclusive_lease_guard_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe ExclusiveLeaseGuard, :clean_gitlab_redis_shared_state do
+  subject :subject_class do
+    Class.new do
+      include ExclusiveLeaseGuard
+
+      def self.name
+        'ExclusiveLeaseGuardTestClass'
+      end
+
+      def call(&block)
+        try_obtain_lease do
+          internal_method(&block)
+        end
+      end
+
+      def internal_method
+        yield
+      end
+
+      def lease_timeout
+        1.second
+      end
+    end
+  end
+
+  describe '#try_obtain_lease' do
+    let(:subject) { subject_class.new }
+
+    it 'obtains the lease, calls internal_method and releases the lease', :aggregate_failures do
+      expect(subject).to receive(:internal_method).and_call_original
+
+      subject.call do
+        expect(subject.exclusive_lease.exists?).to be_truthy
+      end
+
+      expect(subject.exclusive_lease.exists?).to be_falsey
+    end
+
+    context 'when the lease is already obtained' do
+      before do
+        subject.exclusive_lease.try_obtain
+      end
+
+      after do
+        subject.exclusive_lease.cancel
+      end
+
+      it 'does not call internal_method but logs error', :aggregate_failures do
+        expect(subject).not_to receive(:internal_method)
+        expect(Gitlab::AppLogger).to receive(:error).with('Cannot obtain an exclusive lease. There must be another instance already in execution.')
+
+        subject.call
+      end
+    end
+
+    context 'with overwritten lease_release?' do
+      subject :overwritten_subject_class do
+        Class.new(subject_class) do
+          def lease_release?
+            false
+          end
+        end
+      end
+
+      let(:subject) { overwritten_subject_class.new }
+
+      it 'does not release the lease after execution', :aggregate_failures do
+        subject.call do
+          expect(subject.exclusive_lease.exists?).to be_truthy
+        end
+
+        expect(subject.exclusive_lease.exists?).to be_truthy
+      end
+    end
+  end
+
+  describe '#exclusive_lease' do
+    it 'uses the class name as lease key' do
+      expect(Gitlab::ExclusiveLease).to receive(:new).with('exclusive_lease_guard_test_class', timeout: 1.second)
+
+      subject_class.new.exclusive_lease
+    end
+
+    context 'with overwritten lease_key' do
+      subject :overwritten_class do
+        Class.new(subject_class) do
+          def lease_key
+            'other_lease_key'
+          end
+        end
+      end
+
+      it 'uses the custom lease key' do
+        expect(Gitlab::ExclusiveLease).to receive(:new).with('other_lease_key', timeout: 1.second)
+
+        overwritten_class.new.exclusive_lease
+      end
+    end
+  end
+
+  describe '#release_lease' do
+    it 'sends a cancel message to ExclusiveLease' do
+      expect(Gitlab::ExclusiveLease).to receive(:cancel).with('exclusive_lease_guard_test_class', 'some_uuid')
+
+      subject_class.new.release_lease('some_uuid')
+    end
+  end
+
+  describe '#renew_lease!' do
+    let(:subject) { subject_class.new }
+
+    it 'sends a renew message to the exclusive_lease instance' do
+      expect(subject.exclusive_lease).to receive(:renew)
+      subject.renew_lease!
+    end
+  end
+end