Specs for workflow_image_fenerator

fix SCI-2924

spec/services/workflow_image_generator_spec.rb

@@ -3,4 +3,20 @@
 require 'rails_helper'
 
 describe WorkflowImageGenerator do
+  let(:experiment) { create :experiment_with_tasks }
+  let(:params) { { experiment_id: experiment.id } }
+
+  context 'when succeed' do
+    it 'succeed? returns true' do
+      expect(described_class.execute(params).succeed?).to be_truthy
+    end
+
+    it 'worklfow image of experiment is updated' do
+      old_filename = experiment.workflowimg_file_name
+      described_class.execute(params)
+      experiment.reload
+
+      expect(experiment.workflowimg_file_name).not_to be == old_filename
+    end
+  end
 end