Which tool should a developer use to author automated tests for custom Lightning web components?

 A developer should use Jest to author automated tests for custom Lightning web components. Jest is a powerful tool with rich features for writing JavaScript tests. It is the recommended testing framework for Lightning web components by Salesforce1. Jest allows the developer to write unit tests in local JavaScript files, run them from the command line or Visual Studio Code, and debug them using breakpoints and watch expressions2. Jest also provides features such as mocking, code coverage, snapshots, and asynchronous testing3.

Option A, Option B, and Option D are incorrect because they are not testing tools, but rather development tools. Visual Studio Code is an integrated development environment(IDE) that supports Lightning web components development with extensions and plugins4. Salesforce CLI is a command line interface that allows the developer to create, deploy, and manage Lightning web components projects5.Salesforce Developer Console is a web-based tool that provides code editing, debugging, and testing features for Apex and Visualforce, but not for Lightning web components. References:

Test Lightning Web Components

Write Jest Tests

Jest Documentation

Visual Studio Code

Salesforce CLI

[Salesforce Developer Console]