Implement ResetProjectCacheService

app/services/reset_project_cache_service.rb

 class ResetProjectCacheService < BaseService
   def execute
+    @project.increment!(:cache_index)
   end
 end

spec/services/reset_project_cache_service_spec.rb

@@ -6,7 +6,23 @@ describe ResetProjectCacheService do
 
   subject { described_class.new(project, user).execute }
 
-  it "resets project cache" do
-    fail
+  context 'when project cache_index is nil' do
+    before do
+      project.cache_index = nil
+    end
+
+    it 'sets project cache_index to one' do
+      expect { subject }.to change { project.reload.cache_index }.from(nil).to(1)
+    end
+  end
+
+  context 'when project cache_index is a numeric value' do
+    before do
+      project.update_attributes(cache_index: 1)
+    end
+
+    it 'increments project cache index' do
+      expect { subject }.to change { project.reload.cache_index }.by(1)
+    end
   end
 end