Enhance error messages in build test

[Petermashaka]

Hello, i'm Mashaka
I noticed that some test assertions in the build (./dist/ and ./dist/stats/ folder tests) lack descriptive error messages.
Currently, when a test fails, it can be unclear which file or folder caused the failure

[francinelucca]

👋🏽 @Petermashaka Can you provide more info/examples here as to what specific issues you're experiencing? Thanks!