The log calls are harmless in this case -- they just log to the console. Learn about the Jest Mock Function and the different strategies for creating and assigning dependencies to the Mock Function in order to track calls, replace implementations, and set … 175 People Used View all course ›› Visit Site Getting Started - Jest. To use the Jest client, we simply create a JestClient object using the JestClientFactory. According to the documentation mockImplementation can also be used to mock class constructors: mock ('dependency') In the case of a React component test, all the … Although this topic is not directly related to writing tests, it’s always good to consider any possible optimizations you can have in your stack. In order to mock a constructor function, the module factory must return a constructor function. I'll be using single-file components here, and I haven't checked whether splitting them into their own HTML, CSS, or js files works or not, so let's assume you're doing that as well.. First, create a MessageList.vue component under src/components: