Nowadays, large-scale software applications are being developed because of the increasing q-commerce or e-commerce conversion rate. Companies extend their service operation areas with the trend of having a super app. As the result of extended functionality brings some risks together. Therefore, software quality is one of the crucial metrics for achieving reliable and faultless software products. One way of achieving software quality is systematic testing, which is often materialized by model-based testing. An example of model-based testing approaches is Event Sequence Graphs (ESGs). Domain specific language is usually a declarative language that provides substantial gain on a restricted business domain. This thesis mainly focuses on the development of a domain specific language (DSL) for ESG building and visualization process with a modularization support for sub-ESGs and decision tables. The ESGs are augmented by decision tables visualized with a vertex and that vertex is visualized with two tables such as property table and property definition table. The use of the proposed DSL is compared with the existing ESG tool called Test Suite Designer (TSD) in areas such as measuring the cost of quality, understanding the value of quality, motivation to achieve quality, and understand how to overcome it. The comparison results obtained through a questionnaire applied to a focus group show that some improvements for both ESG DSL and TSD are necessary.