Developers building Stencil-based component libraries need reliable testing to ensure their components function as expected in various applications. Stencil offers unit and end-to-end testing capabilities, and the integration with WebdriverIO enhances this by providing a comprehensive framework for browser and mobile automation testing. WebdriverIO supports cross-browser testing, real user interactions, and runs tests in environments similar to those used by end-users. It simplifies unit testing by rendering components into a DOM tree and allows mocking of modules to replace functionality during tests. Additionally, WebdriverIO features visual testing, enabling developers to compare baseline images with test results to identify visual discrepancies. These tools collectively help developers create scalable and stable test suites for their Stencil components.