Re: How to avoid circular module dependencies within a distribution?

On 10/17/2016 11:05 PM, David Christensen wrote:
> I have applied a hierarchical module dependency architecture to avoid
> circular dependencies:
> 
> 1.  Modules and test scripts that do not depend upon any other
> modules within the distribution are "dependency level 0".
> 
> 2.  Modules and test scripts that depend only upon level 0 modules
> are level 1.
> 
> 3.  Modules that depend only upon levels 0 through N are level N+1.

Pondering this some more, here is a more accurate statement of the
strategy I have been using to avoid circular dependencies within
distributions (revised rules marked with '*'):

1.  Modules that do not depend upon any other modules within the
distribution are "dependency level 0".

*2.  Modules that depend only upon modules of levels 0 through N-1 are
level N, for levels N=1 and higher.

*3.  Module test scripts shall not depend upon modules of higher level
than the module they are testing.

*4.  Test scripts shall be run in order from lowest to highest level.


It's rule #3 that has been giving me the most trouble.  For example, I
have testing modules up to level 5 that I would like to use when testing
modules of level 0-4.  Rule #3 blocks me.


As I code my test scripts with no outgoing dependencies -- e.g. I do not
'use' or require' test script files in other files -- test scripts
cannot create circular dependencies.  The fact that they are named after
a particular module is for my benefit; but accidental as far as the
tools are concerned.  The file name of a test script has no bearing upon
its dependency level.


So, perhaps rule #3 should be revised.  Here is the proposed strategy:

1.  Modules that do not depend upon any other modules within the
distribution are "dependency level 0".

2.  Modules that depend only upon modules of levels 0 through N-1 are
level N, for levels N=1 and higher.

*3.  Test scripts have a level equal to the highest level module they
depend upon.

4.  Test scripts shall be run in order from lowest to highest level.


I would then write multiple test scripts for each module -- "early" test
scripts of the same level as the module under test and "late" test
scripts that depend upon higher level modules.


Comments are welcome.


David