use constant instead of literal
comment out debug code
return error instead of xml exception for invald xml
add fixtures to support additional tests
change group due to conflict with other fixtures
add more tests identified by coverage report
remove obsolete file
fix end_time check when nil
add missing tests
fix 1.8.7 test incompatibility
Merge pull request #902 from concerto/test_coverage_models

additional installment of model tests