Now, the source code is in "src/", but as I wanted to do tests, I realized that everyone has "src/main" for the actual app code, and "src/test" and "src/androidTest" for testing code. We force this assumption "src"==> "src/main" in the build.gradle, so adding lines like "testImplementation" and "androidTestImplementation" don't really work.

We need to move the source code to "src/main".