Why think unit tests should be in their own source code hierarchy instead of side-by-side

[Tony]

On Friday, 23 March 2018 at 20:43:15 UTC, H. S. Teoh wrote:
>
>> I've worked on a project where the testing was separated from 
>> the code, and it was a liability IMO. Things would get missed 
>> and not tested properly.

That's where Test Driven Development comes in.

>
> Yep.  As I mentioned elsewhere, recently I've had to resort to 
> external testing for one of my projects, and I'm still working 
> on that right now. And already, I'm seeing a liability: rather 
> than quickly locating a unittest immediately following a 
> particular function, now I have to remember "oh which 
> subdirectory was it that the tests were put in? and which file 
> was it that a particular test of this function was done?". It's 
> an additional mental burden to have to keep doing the mapping 
> between current source location <-> test code location (even if 
> it's a 1-to-1 mapping), and a physical burden to have to 
> continually open external files (and typing a potentially long 
> path for them) rather than just "bookmark, jump to end of 
> function, navigate unittest blocks" in the same file.

There are pluses and minuses to both approaches, but I don't 
think that a separate file approach is as difficult as you are 
suggesting. The naming is typically identical to the project 
entities being tested,  with a prefix like "Test_" tacked onto 
the front of the project, modules, classes and functions, making 
finding things straightforward. And most modern editors/IDEs will 
allow multiple files and projects to be open at the same time, 
allowing test code to be opened only once per coding session.