ModCon consists of a web-based front-end (implemented as a Vue.js application) and a server-side back-end (implemented on top of the Node.js JavaScript runtime). The front-end accepts two inputs from users: the target smart contracts and the test-model specifications to drive the model-based testing process. The front-end allows users to specify coverage strategies and configure test generation priority, and the test execution progress can be monitored on-the-fly. The back-end communicates with the front-end through the WebSocket. On the back-end, the model-based testing engine is in charge of smart contract compilation/deployment, model specification analysis, and the customized model-based testing tasks as per users’ requests.