I like to keep test files in the same folder as the thing(s) they're testing. It makes it easy to find specific ones (since the filenames are `utilities.ts` and `utilities.test.ts`, for example) and I don't need to keep extra folders expanded in my IDE's project panel.<p><a href="https://github.com/metaloha/ts-boilerplate">https://github.com/metaloha/ts-boilerplate</a> shows an example boilerplate that includes this.