As of version 1.7.0 (opus_2015.2-client-2) the CRDS source distribution
has been restructured to remove the "fallback cache" and to omit the
test data directory.

The ^/trunk/crds/cache directory and package has been moved to
^/branches/crds_cache_archive and contains only dirty rules.

The builtin cache has been moved to ^/branches/crds_cache_test for testing
purposes and should be set up as an independent subversion checkout one level
above this directory named "crds_cache_test".  Formally crds.cache was used as
a pristing file archive of operational rules.  Now transferred to
^/branches/crds_cache_test, the rules are no longer guaranteed to be prisitine
and may be modified to support the demands of testing.  The function of version
controlling CRDS rules is now relegated to ^/branches/crds_cache_archive which
contains only pristine production rules transcribed from the HST + JWST
archives.

Additionally, the auxilliary "crds/test/data" test data directory required to
run unit tests has been excluded from the source package distribution and is
only installable using a subversion checkout.  This directory contains crontrived
rules, reference files, and datasets for testing CRDS.

Now,  setting up CRDS to run the built-in unit tests can be accomplished as follows:

% svn co https://aeon.stsci.edu/ssb/svn/crds/trunk  CRDS
% svn co https://aeon.stsci.edu/ssb/svn/crds/branches/crds_cache_test crds_cache_test
% cd CRDS
% source envs/hst-crds-dev.csh
% ./runtests

Runtests is configured to install the ^/trunk/crds/tests/data directory
(normally excluded from the source distribution to reduce size) but still
present in the subversion checkout and installable by adding
--include-test-data to the ./install or setup.py install command.

The above configures CRDS to run the built-in unit tests using 3 file sources:

- ^/branches/crds_cache_test
- ^/trunk/crds/test/data
- /grp/crds/cache

/grp/crds/cache is the shared CRDS readonly cache at the Institute (currently
on the Central Store) which currently contains all rules and references for
both JWST and HST.

CRDS/crds/test/data is normally omitted from source code distributions.

^/branches/crds_cache_test is a modified version of
^/branches/crds_cache_archive altered to support unit testing requirements.

Unit tests requiring a server are run against https://hst-crds-dev.stsci.edu
using this setup.
