History for ZopeEnvironment

??changed:
-
ZTC makes the following assumptions about its environment:

  a) The !ZopeTestCase package is installed in the Zope "trunk" inside the 'Testing' 
     module, which is SOFTWARE_HOME/Testing/!ZopeTestCase. Note that the Testing
     module itself is used by ZTC (e.g. the default custom_zodb.py, setting up 
     an empty !DemoStorage, is the one from Testing).

  b) A 'Products' directory exists inside SOFTWARE_HOME and INSTANCE_HOME.

  c) The tests (the 'tests' subdirectories) are located either below a 
     SOFTWARE_HOME or INSTANCE_HOME, typically in Products/!MyCoolProduct/tests.

  d) The weak assumption is that ZTC can just walk up the directory tree from
     'tests', and find a 'Products' directory. This is how INSTANCE_HOME 
     detection works. It regrettably fails on some filesystems when symbolic 
     links are involved; there is a remedy though, read on.


The tricky part is that INSTANCE_HOME has two distinct purposes:

  1) INSTANCE_HOME/lib/python must be added to sys.path and 
     INSTANCE_HOME/Products to Products.__path__.

  2) INSTANCE_HOME/custom_zodb.py must be used to set up a ZODB.


ZTC attempts to resolve this by detecting an INSTANCE_HOME for 1) but leaving
the actual environment variable untouched so 2) works by still pointing into 
SOFTWARE_HOME/Testing.

As soon as I allow you to set INSTANCE_HOME yourself, I lose the ability to 
distinguish whether you mean 1) or 2) or both. 

Before ZTC 0.6.2 the code assumed "both" and did the magic ZEO dance. This was
clearly too surprising.

The behaviour has now changed to 1). 

That way, if your setup does not fit c) or you run into the symbolic link 
problem d), you can solve it by setting INSTANCE_HOME prior to running the 
tests.

ZEO support ("both") is handled separately, through the new environment 
variable ZEO_INSTANCE_HOME.