single-spa-playground
The single-spa playground is a website that helps you get your code working with single-spa. If you don't know what single-spa is, check out this intro video.
The playground website is a step-by-step tutorial that helps you configure things in a GUI and then verify that they are working from right inside the playground. If you have suggestions for improving it, please submit a pull request for file an issue.
Browser extension
Single-spa also has a browser extension that hooks into your browser's dev tools. The extension allows you to view and control single-spa applications on any web page that uses single-spa. Feel free to download the extension, in addition to using the single-spa playground. The two complement each other.