There are project layouts that put implementation files and test files together.

Trailblazer offers you a new, more intuitive file layout in applications.

Instead of grouping by technology, classes and views are structured by concept, and then by technology. A concept can relate to a model, or can be a completely abstract concern such as invoicing.

It’s become increasingly common to divide code into components, rather than by file type. React, for example, allows for the collocation of a components markup and JavaScript. In Svelte, this is taken one logical step further: the Javascript, markup and styling for a component can all exist together in a single `.svelte`​ file