Do you use Web Compiler extension?

You can use Visual Studio's Web Compiler extension to create a bundle.css and test if CSS was compiled successfully.

More information and download at Visual Studio Marketplace.

✅ Figure: Good example - Web Compiler can find missing curly braces

Unfortunately different kinds of errors, like are not caught.

❌ Figure: Bad example - Curly braces in the wrong place, but still compiled successfully

In addition, Gulp is wrongly successful too:

❌ Figure: Bad example - Gulp couldn't find the curly braces error